Organoborane polyamine complex initiator systems and polymerizable compositions made therewith

ABSTRACT

A composition comprises organoborane polyamine complex and polyol. The composition can form a part of a polymerization initiator system that also includes polyisocyanate. The system can be used to initiate polymerization of acrylic monomer and to form a polyurethane/polyurea acrylic adhesive that has exceptionally good adhesion to low surface energy polymers.

This is a divisional of U.S. application Ser. No. 08/956,333, filed Oct.23, 1997 now U.S. Pat. No. 5,994,484, which is a divisional of U.S.application Ser. No. 08/514,190, filed Aug. 11, 1995, now issued U.S.Pat. No. 5,686,544.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to organoborane polyamine complexinitiator systems and, more specifically, to systems in which thecomplex is carried in a polyol, and to systems that includepolyisocyanate. The invention further relates to polymerizablecompositions made therewith, particularly two-part adhesive compositionsthat have independent polyurethane/polyurea and acrylic components whencured. The adhesive compositions have excellent adhesion to a variety ofsubstrates, especially low surface energy polymers.

2. Description of the Related Art

An efficient, effective means for adhesively bonding low surface energyplastic substrates such as polyethylene, polypropylene andpolytetrafluoroethylene (e.g., TEFLON) has long been sought. Thedifficulties in adhesively bonding these materials are well known. See,for example, "Adhesion Problems at Polymer Surfaces" by D. M. Brewisthat appeared in Progress in Rubber and Plastic Technology, volume 1,page 1 (1985). The conventional approaches typically function by: (1)increasing the surface energy of the substrate (to more closely matchthe surface energies of the substrate and the adhesive thereby promotingbetter wetting of the substrate by the adhesive) and/or (2) eliminatingadditives and low molecular weight polymer fractions in the substratethat can migrate to the substrate surface and adversely affect adhesionby forming a weak boundary layer.

As a result, the conventional approaches often use complex and costlysubstrate surface preparation techniques such as flame treatment, coronadischarge, plasma treatment, oxidation by ozone or oxidizing acids, andsputter etching. Alternatively, the substrate surface may be primed bycoating it with a high surface energy material. However, to achieveadequate adhesion of the primer, it may be necessary to first use thesurface preparation techniques described above. All of these techniquesare well known, as reported in Treatise on Adhesion and Adhesives (J. D.Minford, editor, Marcel Dekker, 1991, New York, volume 7, pages 333 to435). The known approaches are frequently customized for use withspecific substrates. As a result, they may not be useful for bonding lowsurface energy plastic substrates generally.

Moreover, the complexity and cost of the presently known approaches donot render them particularly suitable for use by the retail consumer(e.g., home repairs, do-it-yourselfers, etc.) or in low volumeoperations. One vexing problem is the repair of many inexpensiveeveryday household articles that are made of polyethylene, polypropyleneor polystyrene such as trash baskets, laundry baskets and toys.

Consequently, there has been a considerable and long felt need for asimple, easy to use adhesive that can readily bond a wide variety ofsubstrates, especially low surface energy materials, such aspolyethylene, polypropylene and polytetrafluoroethylene, withoutrequiring complicated surface preparation, priming and the like.

While an adhesive that can bond low surface energy plastics is certainlyadvantageous, the commercial utility of such an adhesive would beenhanced if the components thereof could be combined in a convenient mixratio. This would permit facile application of the adhesive usingconventional adhesive dispensers without the need for laborious handweighing and mixing of the different components. However, the convenientmix ratio should not come at the expense of significantly reducedstorage stability or performance. Thus, there is not only a need for anadhesive that can bond low surface energy plastics, but a need for suchan adhesive that can be readily blended in a convenient mix ratiowithout a material reduction in storage stability or performance.

It may be desirable for such adhesives to possess other attributes. Forexample, in certain applications it may be important for the adhesive tobe tough, elastomeric or abrasion resistant, properties typicallyassociated with polyurethane adhesives. In addition, it may be importantto eliminate or reduce low molecular weight components in the adhesivethat could migrate to the interface between the adhesive and thesubstrate. This could adversely affect adhesion by forming a weakboundary layer. Furthermore, if the low molecular weight components aresolvent extractable, adhesive volume could be lost, voids could becreated in the adhesive, and the adhesive and cohesive strength of thebond could be weakened if the bonded article was exposed to solvent.Also, low molecular weight components may be sensitive to water andtheir migration to the adhesive/substrate interface could decrease thehydrolytic stability of the adhesive bond.

As explained more fully hereinbelow, the organoborane polyamine complexinitiator systems and the related compositions of the invention (whichmay include polyisocyanate, polyol, and acrylic monomer that canpolymerize to polyurethane/polyurea acrylic adhesives) not only satisfythese demands but offer many other advantages.

Organoboranes such as tributylborane and triethylborane have beenreported to initiate and catalyze the polymerization of vinyl monomers(see, for example, G. S. Kolesnikov et al., Bull. Acad. Sci. USSR, Div.Chem. Sci. 1957, p. 653; J. Furakawa et al., Journal of Polymer Science,volume 26, issue 113, p.234, 1957; and J. Furakawa et al., Journal ofPolymer Science, volume 28, issue 116, 1958). The organoborane compoundsof the type described in these references are known to be quitepyrophoric in air which complicates facile use.

Chemical Abstracts No. 134385q (volume 80, 1974) "Bonding Polyolefin orVinyl Polymers" reports that a mixture of 10 parts methyl methacrylate,0.2 part tributylborane, and 10 parts poly(methylmethacrylate) was usedto bond polyethylene, polypropylene and poly(vinyl acetate) rods.

U.S. Pat. No. 3,275,611 to E. H. Mottus et al. discloses a process forpolymerizing olefinic compounds (e.g., methacrylate monomers) with acatalyst comprising an organoboron compound, a peroxygen compound, andan amine. The organoboron compound and the amine may be added to thereaction mixture separately or they may be added as a performed complex.

British Patent Specification No. 1,113,722 "Aerobically PolymerisableCompositions," published May 15, 1968 discloses the polymerization ofacrylate monomers through the use of a free-radical catalyst (e.g.,peroxides) and triarylborane complexes having the general formula (R)₃B-Am wherein R is an aryl radical and Am is an amine. The resultingcompositions are reportedly useful as adhesives.

Chemical Abstracts No. 88532r (volume 73, 1970) "Dental Self-curingResin" and the full text paper to which it refers report thattributylborane can be made stable in air by complexing it with ammoniaor certain amines and that the tributylborane can be reactivated with anamine acceptor such as an isocyanate, an acid chloride, a sulfonylchloride, or anhydrous acetic acid. As a result, the complex can be usedto polymerize blends of methyl methacrylate and poly(methylmethacrylate)to provide a dental adhesive.

A series of patents issued to Skoultchi or Skoultchi et al. (U.S. Pat.Nos.: 5,106,928; 5,143,884; 5,286,821; 5,310,835; and 5,376,746)disclose a two part initiator system that is reportedly useful inacrylic adhesive compositions, especially elastomeric acrylic adhesives.The first part of the two part system includes a stable organoboraneamine complex and the second part includes a destabilizer or activatorsuch as an organic acid or an aldehyde.

The adhesive compositions are reportedly particularly useful instructural and semi-structural applications such as speaker magnets,metal-metal bonding, (automotive) glass-metal bonding, glass-glassbonding, circuit board component bonding, selected plastic to metal,glass, wood, etc. bonding, and electric motor magnets. Those plasticsthat may be bonded are not further described.

U.S. Pat. No. 4,043,982 (O'Sullivan et al.) describes a compositionuseful as an adhesive and which includes an acyl or silyl peroxide-typepolymerization initiator (generally dissolved in a volatile solvent), apolymerizable acrylate-isocyanate monomer or oligomer, and an aryl aminepolymerization initiator. The polymerizable acrylate-isocyanate monomeris the reaction product of an organic polyisocyanate with apolymerizable acrylate ester having a hydroxy or a primary or secondaryamino group in the alcoholic moiety.

U.S. Pat. No. 4,721,751 (Schappert et al.) describespolyurea-polyurethane acrylate dispersions which are reportedly usefulas adhesives and sealants. The materials can be prepared by reacting apolyisocyanate with a polyfunctional amine in the presence of a polyol,an ethylenically unsaturated diluent free of active hydrogens, and anactive hydrogen containing polymerizable ethylenically unsaturatedcompound.

U.S. Pat. No. 4,731,416 (Saunders) describes a polyurethane-typeadhesive comprising the reaction product of: (1) a true solution of a(a) copolymer of an α,β-ethylenically unsaturated carboxylic acid and ahydroxyalkyl ester of an α,β-ethylenically unsaturated acid in (b) apolyahl having a molecular weight of at least 200; (2) an organicpolyisocyanate; and (3) a polyahl chain extender having a molecularweight of less than 200.

U.S. Pat. No. 5,021,507 (Stanley et al.) describes an acrylic modifiedreactive urethane hot melt adhesive which can be obtained by adding aurethane prepolymer to low molecular weight polymers formed fromethylenically unsaturated monomers which do not contain active hydrogen.

SUMMARY OF THE INVENTION

In general, this invention pertains to polymerization initiator systemsthat are particularly useful in providing two-part curable compositions,especially those that cure (i.e., polymerize) to polyurethane/polyureaacrylic adhesives. Broadly, and in one aspect of the invention, thepolymerization initiator systems include organoborane polyamine complexand polyol. Preferably, the complex and the polyol form a solution (evenmore preferably a liquid solution) at room temperature.

A variety of organoborane polyamine complexes may be used in theinvention. The following structure is representative of those that aresuitable: ##STR1##

In this structure:

R¹ is an alkyl group having 1 to 10 carbon atoms;

R² and R³ are independently selected from alkyl groups having 1 to 10carbon atoms and phenyl-containing groups;

Am is a polyamine selected from the group consisting of alkyl polyamine,polyoxyalkylenepolyamine, and the reaction product of a diprimaryamine-terminated material and a material having at least two groupsreactive with primary amine, wherein the number of primary amine groupsin the reaction mixture was greater than the number of groups reactivewith primary amine; and

the value of v is selected so as to provide an effective ratio ofprimary amine nitrogen atoms to boron atoms in the complex, which,broadly, is a ratio of about 0.5:1 to 4:1, although a 1:1 ratio is morepreferred.

A wide variety of polyols may be used, including polyether polyols andpolyester polyols. Preferably, the polyol has a hydroxyl functionalityof 2 to 3. Among those polyols which are particularly preferred arepolyalkylene oxide polyols such as polyethylene oxide polyol,polypropylene oxide polyol, polytetramethylene oxide polyol, ethyleneoxide- and propylene oxide-terminated derivatives of these materials,and blends. Poly-ε-caprolactone polyol is a particularly preferredpolyester polyol.

The polymerization initiator systems of the invention further include apolyisocyanate (preferably a diisocyanate). The polyisocyanate isreactive with the polyamine of the complex and can liberate theorganoborane for initiating polymerization of acrylic monomer.Preferably, the number of equivalents of isocyanate functionality isequal to the sum of the number of equivalents of amine functionalityplus the number of equivalents of hydroxyl functionality in thecomposition. As a result, and quite advantageously, condensationpolymerization of the remaining polyisocyanate occurs by reaction withthe polyol so as to form independent but coexisting linear polymers ornetworks of acrylic and polyurethane/polyurea.

The amount of low molecular weight, migratory polyisocyanate-polyaminereaction product in the composition is reduced by forming a linearpolymer or network of polyurethane/polyurea. Otherwise, such migratorycomponents could bloom to the interface between the adhesive compositionand a substrate, which could result in a weak boundary layer, decreasedhydrolytic stability, reduced adhesion and a loss of cohesive strength,especially if these components are solvent extractable. In certainapplications this could be undesirable.

In another aspect, the invention relates to a polymerizable compositioncomprising organoborane polyamine complex, polyol, polyisocyanate, andpolymerizable acrylic monomer. The polymerizable acrylic monomer ispreferably a monofunctional acrylate ester or a monofunctionalmethacrylate ester (including substituted derivatives and blends ofthese materials). A blend of an alkyl acrylate and an alkyl methacrylateis particularly preferred.

Optionally, the polymerizable composition may include a bireactivecompound; i.e., a compound containing both a free-radicallypolymerizable group (preferably (meth)acrylic functionality) and anamine reactive group. The bireactive compound can be directly includedin the adhesive composition or it can be generated in situ; for example,by reacting a hydroxylated (meth)acrylate with the polyisocyanate.

The polymerizable compositions are particularly useful in providing a100% solids, two-part, curable (at room temperature) adhesivecomposition. One part comprises organoborane polyamine complex andpolyol (preferably as a solution). The other part comprisespolymerizable acrylic monomer, polyisocyanate, and optionally,bireactive compound. The polyisocyanate is provided in an amountsufficient to liberate the organoborane for initiating polymerization ofthe acrylic monomer, and for reacting with the polyamine and the polyolto form polyurethane/polyurea. The two parts of the adhesive may bereadily combined in a convenient, commercially useful, whole number mixratio of 1:10 or less, more preferably 1:4, 1:3, 1:2 or 1: 1, such thatthey can be easily used with two-part adhesive dispensers. When cured,these compositions yield a linear polymer or network of acrylic, alinear polymer or network of polyurethane/polyurea that is independentfrom but coexists with the polymerized acrylic, and residualorganoborane and/or organoborane degradation (e.g., by oxidation)by-products. If a bireactive compound has been included, it can link thepolymerized acrylic and polyurethane/polyurea.

The compositions of the invention have excellent adhesion to low surfaceenergy substrates such as polyethylene, polypropylene andpolytetrafluoroethylene. Thus, in another aspect, the invention relatesto bonded composites comprising a first substrate and a second substrate(preferably low surface energy polymeric materials) adhesively bondedtogether by a layer of a cured adhesive composition according to theinvention. Adhesion to such substrates is promoted by using an effectiveamount of the organoborane polyamine complex, which is broadly about0.03 to 1.5 weight % boron, based on the weight of acrylic-groupcontaining components and organic thickener in the polymerizablecomposition, more preferably about 0.08 to 0.5 weight % boron, mostpreferably 0.1 to 0.3 weight % boron.

The solubility of the organoborane polyamine complex in polyol enablesthe provision of two-part adhesives as described above. The complex canbe separated from constituents with which it may react. This can improvethe storage stability of the adhesive composition. Consequently, theinvention also relates to a method of improving the storage stability ofa two-part polymerizable adhesive composition that comprisespolymerizable acrylic monomer, organoborane polyamine complex, and amaterial that reacts with the polyamine for liberating the organoboraneto initiate polymerization of the acrylic monomer (e.g., thepolyisocyanate). The method comprises the steps of:

(a) providing the organoborane polyamine complex;

(b) providing a polyol in which the organoborane polyamine complex issoluble;

(c) forming a solution of the polyol and the organoborane polyaminecomplex; and

(d) preparing a two-part polymerizable adhesive composition in which onepart comprises the material that reacts with the polyamine and all ofthe polymerizable acrylic monomer, and the other part comprises thesolution of the polyol and the organoborane polyamine complex.

As noted above, the amount of migratory polyisocyanate-polyaminereaction product is reduced by forming polyurethane/polyurea.Consequently, the invention also relates to a method for reducing theamount of migratory material in adhesive compositions of the typedescribed above. The method comprises the steps of:

(a) providing a polyisocyanate that is reactive with the polyaminecomponent of the complex;

(b) providing a polyol that is reactive with the polyisocyanate;

(c) permitting the polyisocyanate to react with the polyamine toliberate the organoborane;

(d) initiating polymerization of the acrylic monomer with the liberatedorganoborane and polymerizing the acrylic monomer to form a linearpolymer or network of acrylic; and

(e) permitting the polyamine, polyisocyanate and polyol to react to forma linear polymer or network of polyurethane/polyurea that is independentfrom but coexists with the linear polymer or network of acrylic.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In general, this invention pertains to polymerization initiator systemsthat are particularly useful in providing two-part curable compositions,especially those that cure (i.e., polymerize) to polyurethane/polyureaacrylic adhesives. Broadly, and in one aspect of the invention, thepolymerization initiator systems include organoborane polyamine complexand polyol. As explained below, the polyol is advantageously both acarrier for the organoborane polyamine complex and reactive with otherconstituents of the polymerization initiator system. More specifically,the polymerization initiator systems of the invention comprise and, morepreferably, consist essentially of organoborane polyamine complex,polyol, and polyisocyanate.

The organoborane component of the complex initiates free-radicalpolymerization of acrylic monomer to form an acrylic component. Tostabilize the organoborane against premature oxidation, it is complexedwith polyamine. The organoborane is liberated from the complex byreacting a portion of the polyisocyanate with the polyamine so as toform polyurea. Quite advantageously, condensation polymerization of theremaining polyisocyanate occurs by reaction with the polyol so as toform a polyurethane/polyurea component that is independent from butcoexists with the acrylic. That is, an independent linear polymer ornetwork of polyurethane/polyurea forms, and an independent linearpolymer or network of acrylic forms (which coexist with each other), asopposed to generating a hybrid "urethane-acrylate" material (i.e., amaterial having a urethane backbone with acrylic functionality either onthe backbone or terminally, or a material having an acrylic backbonewith urethane or isocyanate functionality either on the backbone orterminally).

Advantageously, incorporating the polyamine into the polymerizedcomposition reduces the level of low molecular weight components thatcould bloom or migrate to the adhesive/substrate interface. In the caseof an adhesive, this could cause a weak boundary layer, reducedadhesion, and an increased level of extractable components. As explainedbelow, the independent polyurethane/polyurea and acrylic components maybe linked together by a bireactive compound (i.e., a monomer having bothamine-reactive and free-radically polymerizable functionalities) toprovide more rapid strength build-up and even further reduce the levelof low molecular weight migratory components.

The polyurethane/polyurea acrylic adhesives of the invention can bond awide variety of substrates, but provide exceptionally good adhesion tolow surface energy plastic substrates (e.g., polyethylene,polypropylene, polytetrafluoroethylene, etc.) that, heretofore, havebeen bonded using complex and costly surface preparation techniques.

The polymerized polyurethane/polyurea acrylic compositions derive theiradhesion, especially to low surface energy plastics, from theorganoborane-initiated free-radical polymerization of the acrylicmonomer. The compositions derive their cohesive strength from thesimultaneous organoborane-initiated polymerization of acrylic monomer,and the condensation polymerization of polyisocyanate with the polyolcarrier for the complex and the polyamine from the complex. Mostadvantageously, the compositions of the invention offer both goodadhesion from the polymerized acrylic, and a tough, elastomeric,abrasion resistant bond from the polyurethane/polyurea.

The polyol, polyisocyanate and acrylic monomer are, individually,reactive materials with molecular weights (or weight average molecularweights) of less than about 3,000, more preferably less than about1,000, and most preferably less than about 750. As a result, theinvention also provides a fully reactive, 100% solids, polymerizableadhesive composition. Moreover, the polyol carrier enables the provisionof a storage stable initiator system that can be directly combined withpolymerizable monomers for a two-part adhesive in a convenient,commercially useful, whole number mix ratio of 1:10 or less.

Organoborane polyamine complexes useful in the invention are complexesof organoborane and polyamine. They preferably have the followinggeneral structure: ##STR2## where R¹ is an alkyl group having 1 to 10carbon atoms, and R² and R³ are independently selected from alkyl groupshaving 1 to 10 carbon atoms and phenyl-containing groups. Morepreferably, R¹, R² and R³ are alkyl groups having 1 to 5 carbon atomssuch as methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl, andpentyl. By "independently selected" it is meant that R² and R³ may bethe same or that they may be different. R¹ may be the same as R² or R³,or it may be different. Preferably R¹, R² and R³ are the same. Mostpreferred are complexes in which R¹, R² and R³ are each ethyl groups.

The value of v is selected so as to provide an effective ratio ofprimary amine nitrogen atoms to boron atoms in the complex. The primaryamine nitrogen atom to boron atom ratio in the complex is broadly about1:1 to 4:1. Preferably, however, the ratio is about 1:1 to 2:1, morepreferably about 1:1 to 1.5:1, and most preferably about 1:1. (In thecase of a polyamine that contains both primary and secondary aminegroups, the ratio of primary amine nitrogen atom to boron atom could beas low as 0.5:1.) A primary amine nitrogen atom to boron atom ratio ofless than 1:1 could leave free organoborane, a material that tends to bepyrophoric. At primary amine nitrogen atom to boron atom ratios inexcess of 2:1, the practical utility of the complex in, for example, anadhesive system diminishes as the amount of complex that must beemployed to generate a useful adhesive becomes larger.

"Am" represents the polyamine portion of the complex and may be providedby a wide variety of materials having more than one amine group,including blends of different polyamines. More preferably, the polyaminehas two to four amine groups, although polyamines with two amine groups(i.e., diamines) are most preferred.

In one embodiment, the polyamine may be described by the structure H₂N--R⁴ --NH₂ in which R⁴ is a divalent, organic radical comprised of analkyl, aryl or alkylaryl group. Preferred among these materials arealkane diamines which may be branched or linear, and having the generalstructure ##STR3## in which x is a whole number greater than or equal to1, more preferably about 2 to 12, and R⁵ is hydrogen or an alkyl group,preferably methyl. Particularly preferred examples of alkane diaminesinclude 1,2-ethanediamine, 1,3-propanediamine, 1,5-pentanediamine,1,6-hexanediamine, 1,12-dodecanediamine, 2-methyl-1,5-pentane diamine,3-methyl-1,5-pentane diamine, and isomers of these materials. Whilealkane diamines are preferred, other alkyl polyamines may be used suchas triethylene tetraamine and diethylene triamine.

The polyamine may also be provided by a polyoxyalkylenepolyamine.Polyoxyalkylenepolyamine useful in making complexes for the inventionmay be selected from the following structures:

    H.sub.2 NR.sup.6 O--(R.sup.7 O).sub.w --(R.sup.8 O).sub.x --(R.sup.7 O).sub.y --R.sup.6 NH.sub.2

(i.e., polyoxyalkylene diamines); or

    [H.sub.2 NR.sup.6 O--(R.sup.7 O).sub.w ].sub.z --R.sup.9

R⁶, R⁷ and R⁸ are alkylene groups having 1 to 10 carbon atoms and may bethe same or may be different. Preferably, R⁶ is an alkyl group having 2to 4 carbon atoms such as ethyl, n-propyl, iso-propyl, n-butyl oriso-butyl. Preferably, R⁷ and R⁸ are alkyl groups having 2 or 3 carbonatoms such as ethyl, n-propyl or iso-propyl. R⁹ is the residue of apolyol used to prepare the polyoxyalkylenepolyamine (i.e., the organicstructure that remains if the hydroxyl groups are removed). R⁹ may bebranched or linear, and substituted or unsubstituted (althoughsubstituents should not interfere with oxyalkylation reactions).

The value of w is ≧1, more preferably about 1 to 150, and mostpreferably about 1 to 20. Structures in which w is 2, 3 or 4 are usefultoo. The value of x and y are both ≧0. The value of z is >2, morepreferably 3 or 4 (so as to provide, respectively, polyoxyalkylenetriamines and tetraamines). It is preferred that the values of w, x, yand z be chosen such that the resulting complex is a liquid at roomtemperature as this simplifies handling and mixing thereof. Usually, thepolyoxyalkylenepolyamine is itself a liquid. For the polyoxyalkylene,molecular weights of less than about 5,000 may be used, althoughmolecular weights of about 1,000 or less are more preferred, andmolecular weights of about 250 to 1,000 are most preferred.

Examples of particularly preferred polyoxyalkylenepolyamines includepolyethyleneoxidediamine, polypropyleneoxidediamine,polypropyleneoxidetriamine, diethyleneglycolpropylenediamine,triethyleneglycolpropylenediamine, polytetramethyleneoxidediamine,polyethyleneoxide-co-polypropyleneoxidediamine, andpolyethyleneoxide-co-polyproyleneoxidetriamine.

Examples of suitable commercially available polyoxyalkylenepolyaminesinclude various JEFFAMINES from Huntsman Chemical Company such as the D,ED, and EDR series diamines (e.g., D-400, D-2000, D-5000, ED-600,ED-900, ED-2001, and EDR-148), and the T series triamines (e.g., T-403),as well as H221 from Union Carbide Company.

The polyamine may also comprise the condensation reaction product ofdiprimary amine-terminated material (i.e., the two terminal groups areprimary amine) and one or more materials containing at least two groupsreactive with primary amine (referred to herein at times as"difunctional primary amine-reactive material"). Such materials arepreferably substantially linear so as to have the following generalstructure E--(L--E)_(u) --L--E in which each E is the residue of thediprimary amine-terminated material and each L is a linking group thatis the residue of the difunctional primary amine-reactive material. (By"residue" is meant those portions of the diprimary amine-terminatedmaterial and the difunctional primary amine-reactive material thatremain after reaction to form the polyamine adduct.)

The E and L groups are independently selected. That is, each E group maybe the same or may be different, as may each L group, although it ispreferred that each E group be the same and that each L group be thesame. Preferably E and L are selected so as to form a complex that issoluble in acrylic monomer. The majority (more than 50%) of the terminalgroups in the polyamine should be primary amine.

The value of u is selected so as to provide both a polyamine and acomplex of useful viscosity. Preferably both the polyamine and thecomplex are liquid at room temperature. ("Room temperature" refers to,herein, a temperature of about 20 to 22° C.) Consequently, the value ofu may be greater than or equal to zero, although a value of about 0 to 5is more preferred, and a value of 0 or 1 is most preferred.

The diprimary amine-terminated material may be alkyl diprimary amine,aryl diprimary amine, alkylaryl diprimary amine, apolyoxyalkylenediamine (such as those described above), or mixturesthereof Useful alkyl diprimary amines include those having the structureNH₂ --R¹⁰ --NH₂ wherein R¹⁰ is a linear or branched alkyl group havingabout 1 to 12 carbon atoms such as 1,3-propane diamine,1,6-hexanediamine, and 1,12-dodecanediamine. Other useful alkyldiprimary amines include triethylene tetraamine and diethylene triamine.Examples of useful aryl diprimary amines include 1,3- and 1,4-phenylenediamine as well as the various isomers of diaminonaphthalene. An exampleof a useful alkylaryl diprimary amine is m-tetramethylxylene diamine.

Difunctional primary amine-reactive materials contain at least twogroups reactive with primary amine. The reactive groups may bedifferent, but it is preferred that they be the same. Difunctionalprimary amine-reactive materials having a functionality of 2 (i.e., twogroups reactive with primary amine) are preferred. Useful difunctionalprimary amine-reactive materials may be generally represented by theformula Y--R¹¹ --Z wherein R¹¹ is a divalent organic radical such as analkyl, aryl or alkylaryl group or combination thereof, and Y and Z aregroups reactive with primary amine and which may be the same or may bedifferent. Examples of useful Y and Z groups reactive with primary amineinclude carboxylic acid (--COOH), carboxylic acid halide (--COX, where Xis a halogen, for example chlorine), ester (--COOR), aldehyde (--COH),epoxide ##STR4## amine alcohol (--NHCH₂ OH), and acrylic ##STR5##

Suitable carboxylic acid-functional materials are preferably those whichare useful in forming polyamides, for example,cyclohexane-1,4-dicarboxylic acid and dicarboxylic acids having thestructure HOOC--R¹² --COOH in which R¹² is a linear alkyl group havingabout 2 to 21 carbon atoms. Aromatic dicarboxylic acids (e.g.,terephthalic and isophthalic acids) may be used as can alkylaryldicarboxylic acids, especially in combination with alkyl dicarboxylicacids.

Useful carboxylic halide acid-functional materials and ester-functionalmaterials include those which are obtained by derivatizing theabove-described carboxylic acid-functional materials.

Suitable aldehyde-functional materials include alkyl, aryl and alkylaryldialdehydes such as oxaldehyde propanedialdehyde, succinaldehyde,adipaldehyde, 2-hydroxyhexanedial, phthalaldehyde,1,4,benzenediacetaldehyde, 4,4(ethylenedioxy) dibenzaldehyde, and2,6-naphthalene dicarbaldehyde. Most preferred are glutaraldehyde andadipaldehyde.

Suitable epoxide-functional materials include aliphatic, cycloaliphaticand glycidyl ether diepoxides. Most preferred are the diepoxides basedupon bis-phenol A and bis-phenol F.

Useful acrylic-functional materials are preferably diacrylates and awide variety of such materials may be successfully employed in theinvention.

The organoborane polyamine complex may be readily prepared using knowntechniques. Typically, the polyamine is combined with the organoboranein an inert atmosphere with slow stirring. An exotherm is often observedand cooling of the mixture is, therefore, recommended. If theingredients have a high vapor pressure, it is desirable to keep thereaction temperature below about 70° to 80° C. Once the materials havebeen well mixed the complex is permitted to cool to room temperature. Nospecial storage conditions are required although it is preferred thatthe complex be kept in a capped vessel in a cool, dark location.

The organoborane polyamine complex is employed in an effective amount,which is an amount large enough to permit acrylic monomer polymerizationto readily occur to obtain an acrylic polymer of high enough molecularweight for the desired end use. If the amount of organoborane polyaminecomplex is too low, then the polymerization may be incomplete or, in thecase of adhesives, the resulting composition may have poor adhesion. Onthe other hand, if the amount of organoborane polyamine complex is toohigh, then the polymerization may proceed too rapidly to allow foreffective mixing and use of the resulting composition.

Large amounts of complex could also lead to the generation of largevolumes of borane, which, in the case of an adhesive, could weaken thebondline. The useful rate of polymerization will depend in part on themethod of applying the composition to a substrate. Thus, a faster rateof polymerization may be accomodated by using a high speed automatedindustrial adhesive applicator rather than by applying the compositionwith a hand applicator or by manually mixing the composition.

Within these parameters, an effective amount of the organoboranepolyamine complex is an amount that preferably provides about 0.03 to1.5 weight % boron, more preferrably about 0.08 to 0.5 weight % boron,most preferably about 0.1 to 0.3 weight % boron. The weight % of boronin a composition is based on the total weight of the acrylicgroup-containing materials plus organic thickener, (e.g., poly(methylmethacrylate) or core-shell polymer), if present, and does not includethe polyol or polyisocyanate. It may be calculated by the followingequation: ##EQU1##

Quite advantageously, the organoborane polyamine complex is carried by(e.g., dissolved in or diluted by) polyol or blend of polyols reactivewith isocyanate. The polyol should not be reactive toward, coordinate orcomplex the polyamine. Any of a wide variety of polyols that are used tomake polyurethane may be used in the invention including polyetherpolyols and polyester polyols. Such materials are described in variouspublications such as: Polyurethane Elastomers, published by ElsevierApplied Science, London, 1992; Advances in Polyurethane Technology,chapter 3, edited by Buist and Gudgeon, published by John Wiley andSons, New York, 1968; and Polyurethane Handbook, edited by Oertel,published by Hanser Publishers, Munich, 1985.

While useful materials broadly have a hydroxyl functionality greaterthan 1, it is more preferred that the functionality be in the range of 2to 3. The polyol should be soluble in acrylic monomers included in thecomposition. By "soluble" it is meant that no evidence of gross phaseseparation at room temperature is visible to the unaided eye. Similarly,the organoborane polyamine complex should be soluble in the polyolalthough slight warming of a mixture of the complex and the polyol maybe helpful in forming a solution of the two at room temperature.Preferably the polyol is a liquid. Most preferably the organoboranepolyamine complex and polyol form a liquid solution. Quiteadvantageously, substantial amounts (e.g., more than 75% by weight) ofthe complex may be dissolved in polyol, which facilitates the provisionof two-part adhesives that can be combined in a commercially useful mixratio.

Preferably, the polyol is selected so as to provide apolyurethane/polyurea component having a glass transition temperaturegreater than room temperature, more preferably greater than 30° C. Whilethe hydroxyl groups in the polyol may be secondary or tertiary, polyolshaving primary hydroxyl groups are preferred so as to tailor the rate ofthe polyurethane polymerization to a more useful level.

Polyether polyols are particularly preferred for use in the inventionand may comprise the polymerization product of epoxide with either wateror polyhydric alcohol. Illustrative epoxides that may be employed in thepreparation of polyether polyols useful in the invention include shortchain (e.g., about 2 to 6 carbon atoms) alkylene oxides such as ethyleneoxide, propylene oxide, butylene oxide and amylene oxide; glycidylethers such as t-butyl glycidyl ether and phenyl glycidyl ether; andrandom or block copolymers of two or more of these epoxides.

Exemplary polyhydric alcohols that may be employed in making polyetherpolyols suitable for use in the invention preferably have from two toeight hydroxyl groups and include short chain diols (e.g., having about2 to 7 carbon atoms) such as ethylene glycol, 1,2-propane diol,1,4-butane diol, 1,3-butane diol, 1,5-pentane diol, and 1,7-heptanediol; compounds derived from phenols such as bis-phenol A; and materialshaving more than two hydroxyl groups such as gycerol,1,1,1-trimethylolpropane, 1,1,1-trimethylolethane, hexane-1,2,6-triol,α-methyl glucoside, pentaerythritol, pentatols, hextols, and varioussugars (e.g., glucose, sucrose, fructose and maltose).

As a subclass, polyalkylene polyether polyols (sometimes referred toherein as polyalkylene oxide polyols) are preferred. They may beprepared from the short chain alkylene oxides described previously aswell as other starting materials such as tetrahydrofuran andepihalohydrins such as epichlorohydrin. Alkylene oxide tetrahydrofurancopolymers may also be used. Also useful are arylene oxides such asstyrene oxide which can be used to form polyarylene oxide polyols. Themost preferred polyalkylene polyether polyols are polypropylene oxidepolyol, polyethylene oxide polyol, and polytetramethylene oxide polyol,including ethylene oxide or propylene oxide-terminated derivativesthereof. Most preferred are polypropylene oxide polyols. Examples ofuseful, commercially available polyalkylene polyether polyols includethe REZOL family of materials from Witco Chemical Co. (e.g, ET-700) andthe ARCOL family of materials from ARCO Chemical Co. (e.g., PPG 425 andPPG 1000).

Polyester polyols are also useful and may be prepared by reacting one ormore diols with one or more dicarboxylic acids. Diols which may be usedto make polyester polyols useful in the invention include saturateddiols having the general structure HO--(CH₂)_(x) --OH where the integralvalue of x is about 2 to 6, examples of which include ethylene glycol,propylene glycol, 1,4-butane diol, and 1,6-hexane diol. Dicarboxylicacids which may be used to make polyester polyols useful in theinvention include saturated dicarboxylic acids having the generalstructure HOOC--(CH₂)_(y) --COOH where the integral value of y is about4 to 8, examples of which include adipic acid and sebacic acid. Aromaticdicarboxylic acids may also be used so long as the organoboranepolyamine complex remains soluble therein. Examples of suitablecommercially available polyester polyols include the FOMREZ family ofmaterials from Witco Chemical Co. (e.g., 1066-187).

Polyester polyols based on poly-ε-caprolactone are particularlypreferred and can be obtained from a ring-opening polymerization ofε-caprolactone. The TONE family of poly-ε-caprolactone polyols fromUnion Carbide Corp. (e.g., TONE 0210, 0305 and 0310) are particularlyuseful.

As noted above, the polymerization initiator systems of the inventioninclude a polyisocyanate (i.e., a material having an isocyanatefunctionality greater than 1, more preferably an isocyanatefunctionality of 2 to 4, most preferably an isocyanate functionality of2.). The polyisocyanate reacts with the polyamine of the organoboranepolyamine complex, thereby removing the organoborane from chemicalattachment with the polyamine and forming polyurea. The organoborane isavailable to initiate the free-radical polymerization of acrylicmonomers. Quite advantageously, however, the polyisocyanate is alsoreactive with the polyol which carries the organoborane polyaminecomplex and polymerizes to a linear polymer or network ofpolyurethane/polyurea. As a result, the invention provides a fullyreactive, 100% solids polymerizable composition.

Desirable polyisocyanates readily form reaction products with polyamineand polyol at or below (and, more preferably, at) room temperature so asto provide a composition such as an adhesive that can be easily used andcured under ambient conditions. Polyisocyanates useful in the inventionare soluble in acrylic monomers used in the adhesive composition, bywhich it is meant that no evidence of gross phase separation at roomtemperature is visible to the unaided eye.

Polyisocyanates useful in the invention include various aliphatic,cycloaliphatic, aromatic, and mixed (cyclo)aliphatic-aromaticdiisocyanates. In general, aliphatic diisocyanates are preferred,especially in conjunction with organoborane polyamine complexes thatincorporate aliphatic polyamines.

Among the useful diisocyanates are ethylene diisocyanate, ethylidenediisocyanate, propylene diisocyanate, butylene diisocyanate,hexamethylene diisocyanate (including dimers and trimers thereof),dichlorohexamethylene diisocyanate, cyclopentylene-1,3-diisocyanate,cyclohexylene-1,4-diisocyanate, cyclohexylene-1,2-diisocyanate,isophorone diisocyanate, furfurylidene diisocyanate, toluenediisocyanate, 2,2-diphenylpropane-4,4'diphenylmethane diisocyanate,p-phenylene diisocyanate, m-phenylene diisocyanate, xylylenediisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylenediisocyanate, m-tetramethyl xylylene diisocyanate, polymeric versions of4,4'-methylene diphenyl diisocyanate, diphenyl-4,4'diisocyanate,azobenzene-4,4'diisocyanate, diphenylsulphone-4,4'-diisocyanate, and 1-chlorobenzene-2,4-diisocyanate. Highly crystalline aromatic materialsthat are insoluble in acrylic monomer (e.g., pure 4,4'-methylenediphenyldiisocyanate) would not be used.

Various tri- and tetraisocyanates may also be used such as4,4',4"-triisocyanatotriphenylmethane, 1,3,5-triisocyanatobenzene,2,4,6-triisocyanatotoluene, and4,4'dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate.

Hexamethylene diisocyanate (and its dimers), isophorone diisocyanate,and m-tetramethyl xylylene diisocyanate are preferred.

The polyisocyanate is employed in an effective amount; that is, anamount effective to promote both acrylic monomer polymerization byliberating organoborane from the complex and to permit the formation ofa polyurethane/polyurea of sufficient molecular weight for the intendedend use (but without materially adversely affecting the properties ofthe ultimate polymerized composition). The amount of polyisocyanateemployed is typically in the same range as conventionally used forcondensation polymerization of polyurethane/polyurea.

Larger amounts of polyisocyanate may permit the acrylic monomerpolymerization to proceed too quickly and, in the case of adhesives, theresulting materials may demonstrate inadequate adhesion to low energysurfaces. Undesirable side reactions that adversely affect theperformance properties of the polymerized composition, or an undesirablyhigh level of extractables in the polymerized composition may alsoresult from using large amounts of polyisocyanate that otherwise remainunreacted. If small amounts of polyisocyanate are employed, the rate ofpolymerization may be too slow and the monomers that are beingpolymerized may not adequately increase in molecular weight. However, areduced amount of polyisocyanate may be helpful in slowing the rate ofpolymerization if it is otherwise too fast.

Within these parameters, the polyisocyanate may be provided in an amountwherein the number of equivalents of isocyanate is stoichiometric withthe number of equivalents of amine functionality plus the number ofequivalents of hydroxyl functionality in the polymerizable composition(whether or not they are provided by the polyamine, the polyol, and thepolyisocyanate or other amine-, hydroxyl- or isocyanate-functionalmaterials in the composition).

Optionally, the adhesive composition may contain a bireactive compoundin order to link the polyurethane/polyurea and acrylic. The bireactivecompound preferably comprises at least one free-radically polymerizablegroup and at least one group reactive with amine. Examples of bireactivecompounds useful in the invention can be represented by the followinggeneral structure:

    (Fp).sub.a --Y--(A).sub.b

wherein "Fp" is a free-radically polymerizable group; "A" is anamine-reactive group; "Y" is a polyvalent organic linking group; "a"represents the number of free-radically polymerizable groups; and "b"represents the number of amine-reactive groups.

Free-radically polymerizable group "Fp" preferably comprises an alkenegroup. The alkene group may be unsubstituted or substituted or part of acyclic ring structure. Substituted alkenes include those alkenes havingalkyl or aryl group substitution. Preferred alkenes are those havingterminal unsubstituted double bonds such as allyl groups. Even morepreferred alkenes are styryls. The most preferred alkenes areacrylic-group containing materials. Amine-reactive group "A" preferablycomprises an isocyanate group. Because the bireactive compound comprisesat least one free radically polymerizable group and at least oneamine-reactive group, the value of each of "a" and "b" is at least one.Preferably, the sum of "a" and "b" is less than or equal to six, morepreferably less than or equal to four, most preferably two. Polyvalentorganic linking group "Y" may comprise a wide variety of differentchemical structures depending on the reagents used to prepare thebireactive compound.

Preferably, the bireactive compound comprises the reaction product of apolyisocyanate and a hydroxyl compound containing a free-radicallypolymerizable group. Polyisocyanates useful in forming the bireactivecompound include those discussed above as suitable for reacting with thepolyamine portion of the organoborane polyamine complex.

Adducts prepared by reacting a molar excess of polyisocyanate with anactive hydrogen containing compound (e.g., polyols, polythiols, andpolyamines) are also useful in preparing the the bireactive compound.Useful polyols include alkylene glycols, alkylene ether glycols and,polyhydroxy alkanes. Useful polythiols include 1,3-propanedithiol,2,2'-dimercapto diethyl ether, 2,2'-dimercapto diethyl sulfide,triethylene glycol dimercaptan, and trimethylolethanetri(3-mercaptopropionate). Useful polyamines include ethylenediamine,1,3-diaminopropane, 1,6-hexanediamine, and 4,7,10-trioxa-1,13-tridecanediamine.

Preferred hydroxyl compounds include hydroxylated (meth)acrylates and(meth)acrylamides, wherein the use of the parenthetical expression"(meth)" indicates that the methyl substitution is optional. Adducts ofhydroxylated (meth)acrylates or (meth)acrylamides with lactones (e.g.,ε-caprolactone), so as to form hydroxy(meth)acrylate polyesters, arealso particularly useful.

The most preferred bireactive compounds comprise the reaction product ofthe preferred polyisocyanates referred to above and a hydroxylated(meth)acrylate such as hydroxyethylmethacrylate, hydroxyethylacrylate,hydroxybutylacrylate or adducts of these hydroxylated (meth)acrylateswith ε-caprolactone.

The bireactive compound may be included in the adhesive composition as apreformed material or it may be generated in situ. If provided as apreformed material, the starting ingredients (for example, hydroxylated(meth)acrylate and diisocyanate) are reacted in the presence of aurethane formation catalyst (such as dibutyltindilaurate) and,optionally, free radical inhibitor (e.g., hydroquinone). As an example,when the starting ingredients are a mono-hydroxylated (meth)acrylate anddiisocyanate, the molar ratio of the former to the latter is preferably0.9-1.1:1; more preferably 1:1, so as to provide an NCO to OH equivalentratio of 2:1.

Alternatively, the bireactive compound may be formed in situ byincluding, for example, the hydroxylated (meth)acrylate, with thepolyisocyanate and acrylic monomer (as explained more fully below), inthe presence of a urethane formation catalyst. In this instance, thetotal amount of polyisocyanate should be increased to account for theadditional hydroxyl functionality contributed by the hydroxylated(meth)acrylate. Thus, the compositions of the invention may also includea compound such as a hydroxylated (meth)acrylate or the others describedabove, which react with polyisocyanate to yield a bireactive compound.

As noted above, the liberated organoborane initiates the free-radicalpolymerization of acrylic monomer. By "acrylic monomer" is meantpolymerizable monomers having one or more acrylic or substituted acrylicmoieties, chemical groups or functionality; that is, groups having thegeneral structure ##STR6## wherein R is hydrogen or an organic radicaland R¹ is an organic radical. Where R and R' are organic radicals, theymay be the same or they may be different. Blends of acrylic monomers mayalso be used. The polymerizable acrylic monomer may be monofunctional,polyfunctional or a combination thereof.

The most useful monomers are monofunctional acrylate and methacrylateesters and substituted derivatives thereof such as hydroxy, amide,cyano, chloro, and silane derivatives as well as blends of substitutedand unsubstituted monofunctional acrylate and methacrylate esters.Particularly preferred monomers include lower molecular weightmethacrylate esters such as methyl methacrylate, ethyl methacrylate,methoxy ethyl methacrylate, hydroxyethyl methacrylate, hydroxypropylmethacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate,and blends thereof.

Both acrylate esters and higher molecular weight methacrylate esters areless preferred for use alone, but can be especially usefully employed asmodifying monomers with predominating amounts of lower molecular weightmethacrylate esters so as to, for example, enhance the softness orflexibility of the ultimate adhesive composition. Examples of suchacrylate esters and higher molecular weight methacrylate esters includemethyl acrylate, ethyl acrylate, isobornyl methacrylate, hydroxypropylacrylate, butyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate,2-ethylhexyl methacrylate, decylmethacrylate, dodecyl methacrylate,tert-butyl methacrylate, acrylamide, N-methyl acrylamide, diacetoneacrylamide, N-tert-butyl acrylamide, N-tert-octyl acrylamide,N-butoxyacrylamide, gamma-methacryloxypropyl trimethoxysilane,2-cyanoethyl acrylate, 3-cyanopropyl acrylate, tetrahydrofurfurylchloroacrylate, glycidyl acrylate, glycidyl methacrylate, and the like.

Particularly preferred are blends of any of the lower molecular weightalkyl methacrylate esters described above with alkyl acrylates having 4to 10 carbon atoms in the alkyl group, such as blends of methylmethacrylate and butylacrylate. Polymerizable compositions of this typemay broadly comprise, based on the total weight of the composition,about 2 to 40 wt. % of the alkyl acrylate and, correspondingly, about 60to 98 wt. % of the alkyl methacrylate.

Another class of polymerizable monomers that are especially useful asmodifiers, such as for improving the creep resistance or temperatureresistance of the ultimate composition, corresponds to the generalformula: ##STR7## R¹³ may be selected from the group consisting ofhydrogen methyl, ethyl, and ##STR8## R¹⁴ may be selected from the groupconsisting of chlorine, methyl and ethyl. R¹⁵ may be selected from thegroup consisting of hydrogen, and ##STR9## The value of a is an integergreater than or equal to 1, more preferably, from 1 to about 8, and mostpreferably from 1 to 4. The integral value of b is greater than or equalto 1, more preferably, from 1 to about 20. The value of c is 0 or 1.

Other acrylic monomers useful as modifying monomers, include ethyleneglycol dimethacrylate, ethylene glycol diacrylate, polyethylene glycoldiacrylate, tetraethylene glycol dimethacrylate, diglycerol diacrylate,diethylene glycol dimethacrylate, pentaerythritol triacrylate,trimethylolpropane trimethacrylate, as well as other polyetherdiacrylates and dimethacrylates.

Other polymerizable monomers that are useful in the invention,particularly as modifying monomers, have the general formula: ##STR10##R¹⁶ may be hydrogen, chlorine, methyl or ethyl; R¹⁷ may be an alkylenegroup with 2 to 6 carbon atoms; and R¹⁸ is (CH₂)_(e) in which e is aninteger of 0 to 8, or one of the following: ##STR11## the phenyl groupbeing substitutable at any one of the ortho, meta or para positions. Thevalue of d is an integer of 1 to 4.

Typical monomers of this class include dimethacrylate of bis(ethyleneglycol) adipate, dimethacrylate of bis(ethylene glycol) maleate,dimethacrylate of bis(ethylene glycol) phthalate, dimethacrylate ofbis(tetraethylene glycol) phthalate, dimethacrylate of bis(tetraethyleneglycol) sebacate, dimethacrylates of bis(tetraethylene glycol) maleate,and the diacrylates and chloroacrylates corresponding to thedimethacrylates, and the like.

Also useful as modifying agents are monomers that areisocyanate-hydroxyacrylate or isocyanate-aminoacrylate reactionproducts. These may be characterized as acrylate terminatedpolyurethanes and polyureides or polyureas. Such monomers have thefollowing general formula: ##STR12## where W is selected from the groupconsisting of --O-- and ##STR13## R¹⁹ is selected from the groupconsisting of hydrogen and lower alkyl groups (e.g., 1 to 7 carbonatoms). T is the organic residue of an active hydrogen-containingacrylic ester, the active hydrogen having been removed and the esterbeing hydroxy or amino substituted on the alkyl portion thereof(including the methyl, ethyl and chlorine homologs). The integral valueof e is from 1 to 6. Q is a mono- or polyvalent organic radical selectedfrom the group consisting of alkyl, alkylene, alkenyl, cycloalkyl,cycloalkylene, aryl, aralkyl, alkaryl, poly(oxyalkylene),poly(carboalkoxyalkylene), and heterocyclic radicals, both substitutedand unsubstituted.

Typical monomers of this class include the reaction product of mono- orpolyisocyanates, for example, toluene diisocyanate, with an acrylateester containing a hydroxy or an amino group in the non-acrylate portionthereof, for example, hydroxyethyl methacrylate.

The compositions may further comprise a variety of optional additives.One particularly useful additive is a thickener such as medium (about100,000) molecular weight polymethyl methacrylate which may beincorporated in an amount of about 10 to 40 weight %, based on the totalweight of the composition. Thickeners may be employed to increase theviscosity of the composition to a more easily room temperature appliedviscous syrup-like consistency.

Another particularly useful additive is an elastomeric material. Thesematerials can improve the fracture toughness of compositions madetherewith which can be beneficial when, for example, bonding stiff, highyield strength materials such as metal substrates that do notmechanically absorb energy as easily as other materials, such asflexible polymeric substrates. Such additives can be incorporated in anamount of about 5% to 35% by weight, based on the total weight of thecomposition.

Certain graft copolymer resins such as particles that comprise rubber orrubber-like cores or networks that are surrounded by relatively hardshells, these materials often being referred to as "core-shell"polymers, are particularly useful elastomeric additives. Most preferredare the acrylonitrile-butadiene-styrene graft copolymers. In addition toimproving the fracture toughness of the composition, core-shell polymerscan also impart enhanced spreading and flow properties to the uncuredcomposition. These enhanced properties may be manifested by a reducedtendency for the composition to leave an undesirable "string" upondispensing from a syringe-type applicator, or sag or slump after havingbeen applied to a vertical surface. Use of more than about 20% of acore-shell polymer additive is desirable for achieving improvedsag-slump resistance.

Another useful adjuvant is an acrylic monomer crosslinking agent.Acrylic monomer crosslinking agents can be used to enhance the solventresistance of the adhesive bond, although certain compositions of theinvention have good solvent resistance even in the absence of externallyadded acrylic monomer crosslinking agents. Typically employed in anamount of about 0.2 to 10 weight % based on the total weight of thecomposition, useful acrylic monomer crosslinkers include the variousdiacrylates referred to above as possible acrylic modifying monomers aswell as other materials. Particular examples of suitable acrylic monomercrosslinking agents include ethylene glycol dimethacrylate, ethyleneglycol diacrylate, triethyleneglycol dimethacrylate, diethylene glycolbismethacryloxy carbonate, polyethylene glycol diacrylate, tetraethyleneglycol dimethacrylate, diglycerol diacrylate, diethylene glycoldimethacrylate, pentaerythritol triacrylate, trimethylolpropanetrimethacrylate, as well as other polyether diacrylates anddimethacrylates.

Peroxides may be optionally included (typically in an amount of about 2%by weight or less, based on the total weight of the acrylate andmethacrylate components) for example, to adjust the speed at which thecompositions polymerize or to complete the acrylic monomerpolymerization.

Catalysts that promote the formation of polyurethane (e.g., dibutyl tindilaurate, stannous octoate, and triethylenetriamine such as DABCO fromAir Products and Chemicals Co., etc.) may also be employed. Acatalytically effective amount is used, which is an amount sufficient toincrease the rate of polyurethane polymerization but withoutaccelerating the polymerization such that the adhesive composition curesso quickly that it becomes difficult to spread under normal roomtemperature application conditions. A typical amount of polyurethaneformation catalyst is less than about 2.0% by weight of the polyol.

Other additives which may be included in the compositions are thosewhich are associated with polyurethane formation such as low molecularweight chain extenders (e.g., 1,4-butane diol, 1,3-propane diamine,etc.) which could be included to influence the nature of thepolyurethane/polyurea, especially the hard segment component thereof.The hard segment of the polyurethane can also be modified by appropriateselection of the polyamine component of the complex. Thus, the polyaminecan serve the dual function of stabilizing the organoborane againstoxidation and providing a polyurethane hard segment.

Small amounts of inhibitors such as hydroquinone may be used, forexample, to prevent or reduce degradation of the acrylic monomers duringstorage. Inhibitors may be added in an amount that does not materiallyreduce the rate of polymerization or the ultimate properties of anadhesive or other composition made therewith, typically about 100-10,000ppm based on the weight of the polymerizable monomers. Other possibleadditives include non-reactive colorants, fillers (e.g., carbon black),etc.

The various optional additives are employed in an amount that does notsignificantly adversely affect the polymerization process or the desiredproperties of compositions made therewith.

Polymerizable adhesive compositions according to the invention may beused in a wide variety of ways, including as sealants, coatings, andinjection molding resins. They may also be used as matrix resins inconjunction with glass and metal fiber mats such as in resin transfermolding operations. They may further be used as encapsulants and pottingcompounds such as in the manufacture of electrical components, printedcircuit boards and the like. Quite desirably, they provide polymerizableadhesive compositions that can bond a diverse myriad of substrates,including polymers, wood, ceramics, concrete, and primed metals.

Polymerizable compositions of the invention are especially useful foradhesively bonding low surface energy plastic or polymeric substratesthat historically have been very difficult to bond without usingcomplicated surface preparation techniques, priming, etc. By low surfaceenergy substrates is meant materials that have a surface energy of lessthan 45 mJ/m², more typically less than 40 mJ/m² or less than 35 mJ/m².Included among such materials are polyethylene, polypropylene,acrylonitrile-butadiene-styrene, and fluorinated polymers such aspolytetrafluoroethylene (TEFLON) which has a surface energy of less than20 mJ/m². (The expression "surface energy" is often used synonymouslywith "critical wetting tension" by others.) Other polymers of somewhathigher surface energy that may be usefully bonded with the compositionsof the invention include polycarbonate, polymethylmethacrylate, andpolyvinylchloride.

The polymerizable compositions of the invention can be easily used astwo-part adhesives. The acrylic monomers are blended as would normallybe done when working with such materials, although they should bethoroughly dried to preclude undesirable reaction between thepolyisocyanate and moisture that could cause foaming and carbon dioxideevolution. The polyisocyanate is usually included in this blend so as toseparate it from the organoborane polyamine complex, thus providing onepart of the two-part composition. The optional bireactive compound (ifpresent) is also added to the first part of the adhesive composition.The organoborane polyamine complex, polyol, and any polyurethaneformation catalyst provide the second part of the composition. The firstand second parts are combined shortly before it is desired to use thecomposition.

For a two-part adhesive such as those of the invention to be most easilyused in commercial and industrial environments, the ratio at which thetwo parts are combined should be a convenient whole number. Thisfacilitates application of the adhesive with conventional, commerciallyavailable dispensers. Such dispensers are shown in U.S. Pat. Nos.4,538,920 and 5,082,147 and are available from Conprotec, Inc. (SalemN.H.) under the tradename "Mixpac."

Typically, these dispensers use a pair of tubular receptacles arrangedside-by-side with each tube being intended to receive one of the twoparts of the adhesive. Two plungers, one for each tube, aresimultaneously advanced (e.g., manually or by a hand-actuated ratchetingmechanism) to evacuate the contents of the tubes into a common, hollow,elongated mixing chamber that may also contain a static mixer tofacilitate blending of the two parts. The blended adhesive is extrudedfrom the mixing chamber onto a substrate. Once the tubes have beenemptied, they can be replaced with fresh tubes and the applicationprocess continued.

The ratio at which the two parts of the adhesive are combined iscontrolled by the diameter of the tubes. (Each plunger is sized to bereceived within a tube of fixed diameter, and the plungers are advancedinto the tubes at the same speed.) A single dispenser is often intendedfor use with a variety of different two-part adhesives and the plungersare sized to deliver the two parts of the adhesive at a convenient mixratio. Some common mix ratios are 1:1, 1:2, 1:4 and 1:10.

If the two parts of the adhesive are combined in an odd mix ratio (e.g.3.5:100), then the ultimate user would probably manually weigh the twoparts of the adhesive. Thus, for best commercial and industrial utilityand for ease of use with currently available dispensing equipment, thetwo parts of the adhesive should be capable of being combined in acommon, whole number mix ratio such as 10:1 or less, more preferably1:4, 1:3, 1:2 or 1:1.

Adhesive compositions of the invention are uniquely suited for use withconventional, commercially available dispensing equipment for two-partadhesives. The unique solubility of the organoborane polyamine complexin polyol can be advantageously used to modify the mix ratio of the twoparts of the adhesive composition to the most commercially importantwhole number values; e.g., 1:10, 1:4, 1:3, 1:2 or 1:1. In addition, theexcellent solubility of the organoborane polyamine complex in polyolpermits the complex to be stored apart from the acrylicmonomer-containing part of the two-part composition. As a result, thetwo parts of the composition have excellent storage stability (at leastseveral weeks) but can still be combined in a commercially useful mixratio. Moreover, the polyisocyanate reacts with the polyol and thepolyamine to form a linear polymer or network of polyurethane/polyureaindependent from the linear polymer or network of acrylic.

Once the two parts have been combined, the composition should be usedquickly, as the useful pot life may be short depending upon the acrylicmonomer mix, the amount of complex, the temperature at which the bondingis to be performed, the presence or absence of a polyurethane formationcatalyst, and the type of hydroxyl groups in the polyol.

The polymerizable composition can be easily applied and cured at roomtemperature. Typically, it is applied to one or both substrates and thenthe substrates are joined together with pressure to force excesscomposition out of the bond line. This also has the advantage ofdisplacing composition that has been exposed to air and that may havebegun to oxidize. In general, the bonds should be made shortly after thecomposition has been applied, preferably within about. 10 minutes. Thetypical bond line thickness is about 0.1 to 0.3 mm. The bonding processcan easily be carried out at room temperature and to improve the degreeof polymerization it is desirable to keep the temperature below about40° C., preferably below 30° C., and most preferably below about 25° C.

Once applied, the composition develops cohesive strength from thesimultaneous polymerization of acrylic monomer (to form a linear polymeror network of acrylic) and the polyisocyanate, polyol and polyamine (toform a linear polymer or network of polyurethane/polyurea independentfrom but coexisting with the linear polymer or network of acrylic).Adhesion is provided by the acrylic component. The bonds will cure to areasonable green strength to permit handling of the bonded componentswithin about 6 to 7 hours. Full strength will be reached in about 24hours under ambient conditions; post-curing with heat (typically about80° C.) may be used if desired. Even more rapid strength build-up isfacilitated by the inclusion of a bireactive compound in thepolymerizing mixture to crosslink the acrylic and polyurethane/polyureawith each other, and the use of aromatic polyisocyanate. In suchsituations, handling strength can be reached in less than 1 hour.

The acrylic monomer, polyamine portion of the complex, polyol andpolyisocyanate should be selected so as to yield a cured adhesive inwhich the independent polyurethane/polyurea and acrylic components arecompatible. By "compatible" it is meant that no evidence of gross phaseseparation of the acrylic and polyurethane/polyurea is visible to theunaided eye at room temperature such that the resulting adhesive bondsare characterized by low cohesive strength and inconsistent adhesion.

The invention will be more fully appreciated with reference to thefollowing nonlimiting examples in which the weights are given as eitherweight percents (weight %), based on the total weight of the compositionwhich is nominally 100 weight %, or grams, the weights (excpet forboron) being reported to two significant digits following the decimalpoint.

Various tradenames and abbreviations used in the examples are definedaccording to the following schedule:

    ______________________________________                                        Abbreviation                                                                    or Tradename Description                                                    ______________________________________                                        BA         n-butyl acrylate                                                     BLENDEX B467 Acrylonitrile-butadiene-styrene terpolymer from                   General Electric Specialty Chemicals, Parkersburg,                            WV                                                                           cm Centimeter                                                                 DBTDL Dibutyltindilaurate                                                     DESMOPHEN 1150 Castor oil based polyether-polyester polyol from                          Bayer.                                                             DYTEK A 2-methyl-1,5-diaminopentane, available from E. I.                      duPont deNemours and Co.                                                     FOMREZ 1066-187 Polyester polyol reaction product of trimethylol                         propane and 1,6-hexanedioic acid, available from                    Witco Chemical Co.                                                           FOMREZ UL-28 Polyurethane formation catalyst, available from                   Witco Chemical Co.                                                           HA n-hexylacrylate                                                            HEMA Hydroxyethylmethacrylate                                                 HMDA 1,6-hexanediamine                                                        in. Inch                                                                      IPDI Isophorone diisocyanate                                                  Lo-PMMA low molecular weight poly (methyl methacrylate)                        from Aldrich Chemical Company                                                μm Micron                                                                  mm Millimeter                                                                 MMA Methylmethacrylate                                                        PMMA 101,000 molecular weight poly (methyl                                     methacrylate-co-ethyl acrylate) with less than 5%                             ethylacrylate from Aldrich Chemical Company                                  PPG 425 Polypropylene oxide polyol having an approximate                       number average molecular weight of about 425,                                 available from Aldrich Chemical Company                                      PPG 1000 Polypropylene oxide polyol having an approximate                      number average molecular weight of about 1000,                                available from Aldrich Chemical Company                                      REZOL ET-700 Polyoxyalkylene polyol commercially available                     from Witco Chemical Co.                                                      TEB Triethylborane                                                            THFMA Tetrahydrofurfurylmethacrylate                                          TMXDI Tetramethylxylenediisocyanate                                           TONE 0210 Poly-ε-caprolactane diol, available from Union                         Carbide Corp.                                                      TONE 0305 Poly-ε-caprolactone triol, available from Union                        Carbide Corp.                                                      TONE 0310 Poly-ε-caprolactone triol, available from Union                        Carbide Corp.                                                    ______________________________________                                    

Synthesis of Organoborane Polyamine Complex

All glassware was washed and fired at 1000° F. or was fired by means ofa Bunsen burner until the glassware glowed orange. A glove box was setup and flushed with nitrogen. The oxygen concentration in the glove boxwas monitored by a Servomex Oxygen analyzer and the syntheses werecarried out in a nitrogen environment that contained less than 100 ppmoxygen.

The glove box contained a pressure equalizing dropping funnel, anelectrical balance, a flask with appropriate stoppers, a stand, and anice bath. The organoborane was weighed into the pressure equalizingdropping funnel and the polyamine was weighed into the flask. Theorganoborane was then added dropwise to the polyamine with stirring andcooling. A mild exotherm was observed and the addition of organoboranewas moderated to control the exotherm. If fuming occurred, theorganoborane addition was slowed until the fuming subsided.

When all of the organoborane had been added, the flask was allowed toequilibrate to room temperature and either a crystalline mass or aliquid resulted. If a crystalline mass resulted, it was heated to 55 °C. by means of an oil bath outside of the glove box until a liquid wasobtained. The liquid was then transferred to a vial that had beenflushed with nitrogen. Unless noted otherwise, the complexes weresynthesized neat with a primary nitrogen atom to boron atom ratio of1:1.

Preparation of Monomer Mixtures

More specific details about the monomer mixtures used in the examplesare given below in conjunction with the individual examples. In general,however, the monomer mixtures were generated by weighing methylmethacrylate, n-butyl acrylate, thickener (e.g., poly(methylmethacrylate) or core shell polymer), and bireactive compound (ifincluded) into a bottle. The monomers were first dried over 4Å molecularsieves. The bottle was sealed, placed on a roller/mixer, and heatedunder an infrared heat lamp that rendered the bottle warm but not hot tothe touch until a solution was obtained. After cooling, polyisocyanatewas added. Usually a clear, colorless moderately viscous liquidresulted. In the Tables, monomer ratios are given as a weight % of themonomer mixture.

Preparation of Curative Mixtures

More specific details about the curative mixtures used in the examplesare given below in conjunction with the individual examples. In general,however, curative mixtures were made by dissolving the organoboranepolyamine complex in polyol, using gentle heat as necessary to dissolvethe complex. Polyurethane formation catalyst (if included) was alsoadded. The polyols were first heated under vacuum to over 100° C. toremove water and then stored over 4Å molecular sieves.

Lap Shear Strength Test Method

Examples that were subsequently evaluated to measure the lap shearstrength of adhesive bonds made therewith were tested as describedbelow. Dimensions in English units are nominal and conversion to metricunits is approximate.

More specifically, the test specimens used were similar to thatdescribed in ASTM D-1002 except that they were generated using fingerpanels of nominal dimensions 1 in.×4 in.×1/8 in. thick (2.5 cm×10.2cm×0.3 cm thick). 0.5 in. (1.3 cm) wide red lithographers tape wasapplied to the end of one of the adherends in order to fixture the bondand also to aid in making the overlap region be 0.5 in. (1.3 cm). Shortpieces of piano wire measuring 0.006 in. (150 μm) diameter for examples1 and 2 and 0.008 in. (200 μm) diameter for all other examples were usedas spacers to control the thickness of the adhesive bondline.

The adhesive composition was made by weighing previously preparedmonomer mixture into a vial that was capable of being sealed with a polycap. Previously prepared curative mixture was then added, blended withthe monomer mixture using a wooden stick, and the vial was sealed withthe poly cap. In general, the addition of the curative mixture to themonomer mixture caused the blend to slightly exotherm and, in somecases, turn yellow.

A dab of the mixed adhesive was applied to each adherend and spread tomake sure that a 1 in.×0.5 in. (2.5 cm×1.3 cm) area was covered at theend of each adherend. Two pieces of piano wire were placed into theadhesive on one adherend and the bond was closed and fixtured with thelithographers tape. The bond was further fixtured with two binder clipsand allowed to cure at room temperature for 48 hours at which time thebinder clips and tape were removed.

Lap shear testing was done with three types of adherends: mechanicalgrade TEFLON, high density polyethylene, and polypropylene, as availablefrom Precision Punch and Plastic Co. (Minneapolis, Minn.). Threeadhesive bonds were made with each adherend and each adhesivecombination. For each adhesive, the TEFLON was bonded first, then thehigh density polyethylene, and then the polypropylene.

After curing, the bonds were tested to failure using a Tensile TestingMachine. The crosshead speed was 0.1 in./minute (2.5 mm/min.) and thetests were carried out at room temperature. The lap shear strengths arean average of the three measurements and are reported in psi (pounds persquare inch) to the nearest whole number.

Bonds were visually inspected after being loaded to failure to determinethe failure mode. Failure of the adherends is the most preferredalthough cohesive failure of the adhesive composition evidences a usefulformulation. Failure modes are reported in the examples based on aseries of coded abbreviations which may be interpreted as follows:

    ______________________________________                                        Abbreviation                                                                              Failure Mode                                                      ______________________________________                                        a           Good filet adhesion                                                 b One or more bonds stretched to yield of the                                  adherend without failure                                                     c Mixed mode failure                                                          d Failure of the adherend                                                     e Cohesive failure within the adhesive                                        f Adhesion failure of the adhesive                                            g Incomplete wetting; puddling of the adhesive                              ______________________________________                                    

EXAMPLE 1

Two adhesive compositions according to the invention were prepared usingthe formulations shown below in Table 1. In Table 1, as in many of theother tables, information pertaining to the adhesive composition isprovided in condensed form with the ingredients identified by theabbreviations shown in the previous schedule and with the relativeamounts of each ingredient given parenthetically. Thus, the first entryin Table 1 describes an adhesive composition in which the monomermixture comprised 34.80 wt. % methyl methacrylate (MMA), 25.20 wt. %n-butyl acrylate (13A), 10.00 wt. % m-tetramethyl xylene diisocyanate(TMXDI), and 30.00 wt. % poly (methyl methacrylate) (PMMA). The curativemixture comprised 17.50 wt. % triethylborane* 1,6-hexane diamine (TEB*HMDA) complex, and 82.50 wt. % DESMOPHEN 1150 polyol.

The adhesive compositions were then tested for lap shear strength andfailure mode using the procedure described above and with the resultsshown below in Table 1. The cohesive failure mode for most of the bondsindicates that adhesion was promoted by the organoborane-initiatedacrylic polymer. The compositions of example 1 are useful inapplications where a softer material is desired, for example, a sealant.A commercially useful 10:1 mix ratio was obtained. The lap shearstrength could be increased by providing a larger amount ofpolyurethane/polyurea.

                                      TABLE 1                                     __________________________________________________________________________    Adhesive Composition    Testing                                                                  Ratio of                                                                           TEFLON  Polyethylene                                                                          Polypropylene                                            Monomer                                                                            Lap     Lap     Lap                                       Mixture to Shear  Shear  Shear                                              Monomer Mixture Curative Mixture Curative Strength Failure Strength                                                     Failure Strength Failure                                                       (Ratio) (Ratio) Mixture                                                      (psi) Mode (psi) Mode (psi)                                                   Mode                              __________________________________________________________________________    MMA/BA/   TEB*HMDA/                                                                              10:1 98  a,c 102 e   184 e                                   TMXDI/PMMA DESMOPHEN                                                          (34.80/25.20/ 1150                                                            10.00/30.00) (17.50/82.50)                                                    MMA/BA/ TEB*HMDA/ 10:1 98 f 246 a,e 124 a,e                                   TMXDI/PMMA PPG1000/PPG425                                                     (34.80/25.20/ (17.50/37.00/                                                   10.00/30.00) 45.50)                                                         __________________________________________________________________________

EXAMPLE 2

A series of adhesive compositions according to the invention wasprepared following the procedure described above and having theformulations shown below Table 2. The last entry in Table 2 is acomparative example which contained neither acrylic monomer nororganoborane polyamine complex. The ratios are given in wt. %. The lapshear strength of the adhesive compositions was tested and the failuremode analyzed as described above and with the results shown in Table

                                      TABLE 2                                     __________________________________________________________________________    Adhesive Composition                                                                             Testing                                                                  Ratio of                                                                           TEFLON  Polyethylene                                                                          Polypropylene                                            Monomer                                                                            Lap     Lap     Lap                                            Mixture to Shear  Shear  Shear                                              Monomer Curative Curative Strength Failure Strength Failure Strength                                               Failure                                  Mixture (Ratio) Mixture (Ratio) Mixture (psi) Mode (psi) Mode (psi)         __________________________________________________________________________                                           Mode                                   MMA/BA/                                                                              TEB*HMDA/                                                                            10:1 296 a,e 646 a,e 374 a,d,e                                    TMXDI/ TONE 305/                                                              PMMA FOMREZ                                                                   (36.50/26.30/ UL-28                                                           7.20/30.00) (34.30/63.80/                                                      2.00)                                                                        MMA/TMXDI/ TEB*HMDA/ 10:0.6 164 a,f 740 a,b,e 678 a,d,e                       PMMA TONE 0305/                                                               (62.80/7.20/ FOMREZ                                                           30.00) UL-28                                                                   (34.30/63.80/                                                                 2.00)                                                                        MMA/TMXDI/ TEB*DYTEK 10:1 256 a,f 570 a,e 490 a,d                             LoPMMA A/                                                                     (64.90/5.10/ TONE 0305/                                                       30.00) FOMREZ                                                                  UL-28                                                                         (31.80/66.30/                                                                 2.00)                                                                        MMA/BA/ TEB*DYTEK 10:1 312 a,e 622 a,e 318 a,d,e                              TMXDI/ A/TONE 0305/                                                           Lo PMMA FOMREZ                                                                (36.70/26.20/ UL-28                                                           7.20/30.00) (31.80/66.30/                                                      2.00)                                                                        MMA/BA/ TEB*HMDA/  4:1 318 a,c,d 642 e 470 d,e                                TMXDI/ TONE 0305/                                                             PMMA FOMREZ                                                                   (30.60/22.00/ UL-28                                                           17.40/30.00) (16.10/82.00/                                                     2.00)                                                                        MMA/BA/ TEB*HMDA/  2:1 250 c 784 b,e 566 e                                    TMXDI/ TONE 0305/                                                             PMMA FOMREZ                                                                   (20.80/14.90/ UL-28                                                           34.20/30.00) (4.60/94.50/                                                      1.00)                                                                        TMXDI TONE 0305/  5:7.35  13 f 146 f  0 f                                     (100.00) FOMREZ                                                                UL-28                                                                         (99.00/1.00)                                                               __________________________________________________________________________

In general, the failure mode was cohesive in the adhesive or theadherend stretched or failed. However, when the acrylic monomers and theorganoborane polyamine complex were removed to provide the comparativeexample, the lap shear strength fell off significantly and the failuremode became adhesive for all substrates. Table 2 shows the use oftrifunctional polyol and polyurethane formation catalysts. Table 2 alsoshows that commercially useful mix ratios of 10:1, 4:1 and 2:1 can beachieved with the adhesive compositions of the invention, indicatingthat they can be readily dispensed with commercially availabledispensers for two-part adhesives.

EXAMPLE 3

A series of adhesive compositions according to the invention wasprepared following the procedure described above and having theformulations shown below in Table 3. The monomer mixture includedhydroxyethylmethacrylate bireactive compound to crosslink thepolymerized acrylate to the polyurethane/polyurea. The component ratios(which are given in wt. %) were adjusted such that the stoichiometry ofisocyanate groups to the combined amount of hydroxyl and amine groupswas equal to 1:1 for each adhesive composition. The lap shear strengthof the adhesive compositions was tested and the failure mode analyzed asdescribed above and with the results shown in Table 3.

                                      TABLE 3                                     __________________________________________________________________________    Adhesive Composition                                                                           Ratio of                                                                           Testing                                                                  Monomer                                                                            TEFLON  Polyethylene                                                                          Polypropylene                                            Mixture                                                                            Lap     Lap     Lap                                         to Shear  Shear  Shear                                                      Monomer Mixture Curative Mixture Curative Strength Failure Strength                                                   Failure Strength Failure                                                       (Ratio) (Ratio) Mixture (psi)                                                Mode (psi) Mode (psi) Mode          __________________________________________________________________________    MMA/BA/HEMA/                                                                           TEB*DYTEK                                                                             10:1 252 c   670 b    976                                                                              b,d                                   IPDI/PMMA/ A/TONE                                                             DBTDL 0305/DBTDL                                                              (41.90/30.20/0.72/ (37.40/62.50/                                              7.14/20.00/0.006) 0.06)                                                       MMA/BA/HEMA/ TEB*DYTEK 10:1 278 c 318 b,e 1014 b,d                            IPDI/PMMA/ A/TONE                                                             DBTDL 0305/DBTDL                                                              (39.10/28.10/3.36/ (37.40/62.50/                                              9.45/20.00/0.03) 0.06)                                                        MMA/BA/HEMA/ TEB*DYTEK 10:1 230 a,f 206 a,e  308 c,d                          IPDI/PMMA/ A/TONE                                                             DBTDL 0305/DBTDL                                                              (36.00/25.90/ (37.40/62.50/                                                   6.20/11.80/20.00/ 0.06)                                                       0.07)                                                                       __________________________________________________________________________

Table 3 shows the improved adhesion that can be obtained when theadhesive composition includes a bireactive compound. Preferably, thebireactive compound is employed in an amount of about 0.5 to 50% basedon the ratio of hydroxyl equivalents to polyisocyanate equivalents.Table 3 also shows that isophorone diisocyanate can be used as thepolyisocyanate and that dibutyltindilaurate can be used as thepolyurethane formation catalyst.

EXAMPLE 4

Example 4 shows an adhesive composition according to the invention inwhich BLENDEX B467 core shell polymer was used as a thickener ratherthan poly(methyl methacrylate). The monomer mixture wasMMA/BA/TMXDI/BLENDEX B467 in which the relative weight percentages ofthe different ingredient was: 52.00/11.30/6.80/30.00. The monomermixture was prepared by mixing the different ingredients in a blenderunder high shear conditions until an off-white opalescent thixotropicmass was obtained. The curative mixture (prepared as described in thecurative mixture preparation) was TEB*HMDA/TONE 0305/FOMREZ UL-28 inwhich the relative weight percentages of the different ingredients was:32.40/67.60/0.0010. The monomer mixture and curative mixture werecombined in a 10:1 ratio and lap shear strength test specimens wereprepared and tested as described above and with the results shown belowin Table 4.

                  TABLE 4                                                         ______________________________________                                        TEFLON       Polyethylene  Polypropylene                                      Lap Shear        Lap Shear       Lap Shear                                      Strength Failure Strength Failure Strength Failure                            (psi) Mode (psi) Mode (psi) Mode                                            ______________________________________                                        340     a,b,e    508      a,e    692    e                                     ______________________________________                                    

EXAMPLE 5

A series of adhesive compositions according to the invention wasprepared in which the monomer mixtures described in Table 5 below werepaired with corresponding curative mixtures shown below in Table 6. Themonomer mixtures and curative mixtures were prepared as described above,although no heat was used. In Tables 5 and 6, the relative amounts ofthe different ingredients are given in grams (g). The lap shear strengthof the adhesive compositions was tested and the failure mode analyzed asdescribed above and with the results shown below in Table 7.

                  TABLE 5                                                         ______________________________________                                                    MMA      BA      HEMA  IPDI  PMMA                                   Monomer Mixture (g) (g) (g) (g) (g)                                         ______________________________________                                        M1          5.77     4.15    1.50  2.57  6.00                                   M2 5.70 4.10 1.58 2.65 6.00                                                   M3 5.50 3.94 1.69 2.89 6.00                                                 ______________________________________                                    

The HEMA included 0.07% by weight DBTDL.

                  TABLE 6                                                         ______________________________________                                                 TEB*DYTEK A             TONE                                           Curative Complex  0305                                                        Mixture (g) N:B Ratio (g)                                                   ______________________________________                                        C1       1.26           1:1      3.74                                           C2 0.75 2:1 4.25                                                              C3 1.83 2:1 3.17                                                            ______________________________________                                    

The Tone 0305 included 0.047% by weight DBTDL. N:B refers to the ratioof primary amine nitrogen atoms to boron atoms in the complex.

As shown below in Table 7 a series of adhesive compositions was preparedin which a monomer mixture was combined with its corresponding curativein a 10:1 weight ratio. When weighed and mixed by hand, the adhesivecompositions cured too quickly to be used. The adhesive compositionswere then used in conjunction with a 10:1 tubular syringe type two-partadhesive dispenser that was outfitted with a static mixer.

Lap shear strength test specimens were prepared as described above butwith several exceptions. Because the adhesive compositions curedrapidly, a stripe of adhesive was placed at the end of one adherend andat the end of the other adherend and the bonds were mated and compressedby hand until the wire spacers resisted further compression. The bondswere made in the following order: TEFLON, polyethylene, polypropylene;TEFLON, polyethylene, polypropylene; TEFLON, polyethylene,polypropylene. After all nine bonds were made, they were fixtured withbinder clips and allowed to cure at room temperature for 48 hours beforelap shear strength testing and bond failure analysis. The test resultsare shown below in Table 7.

                                      TABLE 7                                     __________________________________________________________________________              Testing                                                             Adhesive  TEFLON   Polyethylene                                                                           Polypropylene                                     Composition                                                                             Lap Shear                                                                              Lap Shear                                                                              Lap Shear                                         Monomer                                                                            Curative                                                                           Strength                                                                           Failure                                                                           Strength                                                                           Failure                                                                           Strength                                                                           Failure                                        Mixture Mixture (psi) Mode (psi) Mode (psi) Mode                            __________________________________________________________________________    M1   C1   199  f   656  b   118  a,c,f                                          M2 C2  79 a,f 667 b 313 a,c,f                                                 M3 C3 120 a,f 586 a,b,c 375 c,f                                             __________________________________________________________________________

Table 7 shows that the adhesive compositions of the invention can beused in conjunction with a tubular dual syringe type dispenser fortwo-part adhesives while providing adhesion to various low surfaceenergy polymer surfaces. Example 5 further shows how the adhesivecompositions of the invention can rapidly build strength. They curedquickly to a high lap shear strength.

EXAMPLE 6

A series of adhesive compositions according to the invention wasprepared in which the monomer mixtures described in Table 8 below werepaired with corresponding curative mixtures as shown below in Table 9.The monomer mixtures and curative mixtures were prepared as describedabove. In Tables 8 and 9, the relative amounts of the differentingredients are given in grams.

                  TABLE 8                                                         ______________________________________                                        Monomer                                                                              MMA     BA     THFMA  HA   TMXDI IPDI PMMA                               Mixture (g) (g) (g) (g) (g) (g) (g)                                         ______________________________________                                        M1     10.70   7.67               4.16       7.50                               M2 10.90 7.83    3.78 7.50                                                    M3 11.10 8.00   3.39  7.50                                                    M4 11.30 8.13    3.08 7.50                                                    M5 11.30 8.16   3.01  7.50                                                    M6 11.50 8.27    2.73 7.50                                                    M7  8.00 7.24 2.06  5.20  7.50                                                M8 10.06 5.00  2.24 5.20  7.50                                                M9 10.06 7.24   5.20  7.50                                                    M10 10.34 7.44    4.72 7.50                                                 ______________________________________                                    

                                      TABLE 9                                     __________________________________________________________________________               REZOL                                                                             FOMREZ           TEB*DYTEK                                       Curative TONE 030 ET-700 1066-187 TONE 0210 TONE 0310 A COMPLEX                                              Mixture (g) (g) (g) (g) (g) (g)              __________________________________________________________________________    C1         6.65                 0.85                                            C2  6.64    0.86                                                              C3   6.63   0.87                                                              C4   6.62   0.88                                                              C5    3.31 3.31 0.89                                                          C6    3.31 3.31 0.89                                                          C7 6.69     0.82                                                              C8 6.69     0.82                                                              C9 6.69     0.81                                                              C10 6.67     0.83                                                           __________________________________________________________________________

In curative mixtures C1 to C8, the polyol included 1% by weight DBTDL.In curative mixtures C9 to C10, the polyol included 1% by weight FomrezUL-28. Each complex had a 1:1 ratio of primary amine nitrogen atoms toboron atoms.

As shown below in Table 10 a series of adhesive compositions wasprepared in which a monomer mixture was combined with its correspondingcurative mixture at a 4:1 weight ratio. The lap shear strength of theadhesive compositions was tested and the failure mode analyzed asdescribed above and with the results shown in Table 10.

                                      TABLE 10                                    __________________________________________________________________________              Testing                                                                       TEFLON   Polyethylene                                                                           Polypropylene                                     Adhesive Composition                                                                    Lap Shear                                                                              Lap Shear                                                                              Lap Shear                                         Monomer                                                                            Curative                                                                           Strength                                                                           Failure                                                                           Strength                                                                           Failure                                                                           Strength                                                                           Failure                                        Mixture Mixture (psi) Mode (psi) Mode (psi) Mode                            __________________________________________________________________________    M1   C1    70  c    76  e    96  e                                              M2 C2 178 c 206 e 506 a,d,e                                                   M3 C3 198 c 530 e 890 b,d                                                     M4 C4 208 a,c 594 a,e 1052  b,d                                               M5 C5 174 c 358 a,e 358 a,e                                                   M6 C6 198 c 524 e 968 b,d                                                     M7 C7 234 c 518 b,e 972 b,d                                                   M8 C8 212 c 362 a,e 922 b,d                                                   M9 C9 190 c 634 a,b,e 866 a,b,d,e                                             M10 C10 182 c,f 424 a,e 900 b,d                                             __________________________________________________________________________

Table 10 shows that different polyols, acrylic monomers, polyisocyanatesand polyurethane formation catalysts can be used in the adhesivecompositions of the invention. Curative mixtures C5 and C6 show a blendof liquid and solid polyols, which formed a solution. The flexibility ofthe adhesive can be tailored by appropriate selection of the polyol andacrylic monomer. The combination of monomer mixture M1 and curativemixture C1 had adhesion but was flexible and elastomeric. Othercombinations also adhered but with higher lap shear strength.

EXAMPLE 7

A series of adhesive compositions according to the invention wasprepared in which the monomer mixtures described in Table 11 below werepaired with corresponding curative mixtures shown below in Table 12. Themonomer mixtures and curative mixtures were prepared as described above.In Tables 11 and 12, the relative amounts of the different ingredientsare given in grams.

The amount of organoborane polyamine complex was varied in the adhesivecompositions. In order to maintain a 1:1 stoichiometry (i.e., ratio ofisocyanate groups to the combined number of hydroxyl and amine groups),the level of polyol and polyisocyanate was varied. The polyol included0.05% by weight DBTDL. The ratio of primary amine nitrogen atoms toboron atoms in the complex was 1:1

                  TABLE 11                                                        ______________________________________                                                      MMA     BA       TMXDI PMMA                                       Monomer Mixture (g) (g) (g) (g)                                             ______________________________________                                        M1            12.80   9.20     2.10  6.00                                       M2 12.80 9.20 2.10 6.00                                                       M3 12.80 9.20 2.10 6.00                                                       M4 12.70 9.20 2.10 6.00                                                       M5 12.70 9.20 2.10 6.00                                                       M6 12.70 9.10 2.20 6.00                                                       M7 12.70 9.10 2.20 6.00                                                       M8 12.60 9.10 2.30 6.00                                                     ______________________________________                                    

                  TABLE 12                                                        ______________________________________                                                     TONE    TEB*DYTEK A COMPLEX                                        Curative Mixture (g) (g)                                                    ______________________________________                                        C1           5.92     0.080                                                     C2 5.76 0.24                                                                  C3 5.34 0.66                                                                  C4 5.18 0.82                                                                  C5 4.34 1.66                                                                  C6 3.48 2.52                                                                  C7 2.58 3.42                                                                  C8 1.38 4.62                                                                ______________________________________                                    

As shown below in Table 13 a series of adhesive compositions wasprepared in which a monomer mixture was combined with its correspondingcurative mixture in a 10:1 weight ratio to show how varying the boroncontent in the adhesive composition affects lap shear strength. The lapshear strength of the adhesive compositions was tested and the failuremode analyzed as described above and with 10 the results shown in Table13.

                                      TABLE 13                                    __________________________________________________________________________                  Testing                                                                       TEFLON   Polyethylene                                                                           Polypropylene                                 Adhesive Composition                                                                        Lap Shear                                                                              Lap Shear                                                                              Lap Shear                                     Monomer                                                                            Curative                                                                           Wt. %                                                                             Strength                                                                           Failure                                                                           Strength                                                                           Failure                                                                           Strength                                                                           Failure                                    Mixture Mixture Boron (psi) Mode (psi) Mode (psi) Mode                      __________________________________________________________________________    M1   C1   0.01                                                                               2   f    3   f    13  f                                          M2 C2 0.03  1 f 327 c  30 c                                                   M3 C3 0.08 132 c 378 a,e 484 a,e                                              M4 C4 0.1 110 c 488 e 668 d                                                   M5 C5 0.2  96 c 290 e 466 a,e                                                 M6 C6 0.3 122 c 464 e 486 d,e                                                 M7 C7 0.4 114 a,c 282 e 386 e                                                 M8 C8 0.5 128 c 208 e 424 e                                                 __________________________________________________________________________

Table 13 shows that at boron levels (calculated as a weight percentageof the acrylate-group containing portion of the adhesive compositionplus thickener, i.e., acrylic monomers and poly(methyl methacrylate))below about 0.03 wt. %, adhesion is reduced. At about 0.03 wt. % boronthe adhesion to polyethylene increases. Above about 0.08 wt. % boron,adhesion to all substrates improves. Curative mixture C8 also shows asolution comprising more than 75% by weight organoborane polyaminecomplex.

EXAMPLE 8

A series of adhesive compositions according to the invention wasprepared in which the monomer mixtures described in Table 14 below werepaired with corresponding curative mixtures shown below in Table 15. Themonomer mixtures and curative mixtures were prepared as described above.In Tables 14 and 15, the relative amounts of the different ingredientsare given in grams.

The amount of organoborane polyamine complex was varied in the adhesivecompositions. In order to maintain a 1:1 stoichiometry (i.e., ratio ofisocyanate groups to the combined number of hydroxyl and amine groups),the level of polyol and polyisocyanate was varied. The polyol included1% by weight DBTDL. The ratio of primary amine nitrogen atoms to boronatoms in the complex was 1:1.

                  TABLE 14                                                        ______________________________________                                        Monomer   MMA     BA         TMXDI PMMA                                         Mixture (g) (g) (g) (g)                                                     ______________________________________                                        M1        10.10   7.27       5.12  7.50                                         M2 10.10 7.27 5.13 7.50                                                       M3 10.10 7.26 5.15 7.50                                                       M4 10.10 7.26 5.16 7.50                                                       M5 10.10 7.24 5.19 7.50                                                       M6 10.00 7.22 5.23 7.50                                                       M7 10.00 7.21 5.27 7.50                                                       M8 10.00 7.19 5.32 7.50                                                     ______________________________________                                    

                  TABLE 15                                                        ______________________________________                                                     TONE 0305 TEB*DYTEK A COMPLEX                                      Curative Mixture (g) (g)                                                    ______________________________________                                        C1           7.46       0.040                                                   C2 7.39 0.11                                                                  C3 7.21 0.29                                                                  C4 7.13 0.37                                                                  C5 6.76 0.74                                                                  C6 6.38 1.12                                                                  C7 5.98 1.52                                                                  C8 5.58 1.92                                                                ______________________________________                                    

As shown below in Table 16 a series of adhesive compositions wasprepared in which a monomer mixture was combined with its correspondingcurative mixture in a 4:1 weight ratio to show how varying the boroncontent in the adhesive composition affects lap shear strength. The lapshear strength of the adhesive a compositions was tested and the failuremode analyzed as described above and with the results shown in Table 16.The adhesive compositions nominally comprised more than 40%polyurethane/polyurea.

                                      TABLE 16                                    __________________________________________________________________________                  Testing                                                                       TEFLON   Polyethylene                                                                           Polypropylene                                 Adhesive Composition                                                                        Lap Shear                                                                              Lap Shear                                                                              Lap Shear                                     Monomer                                                                            Curative                                                                           Wt. %                                                                             Strength                                                                           Failure                                                                           Strength                                                                           Failure                                                                           Strength                                                                           Failure                                    Mixture Mixture Boron (psi) Mode (psi) Mode (psi) Mode                      __________________________________________________________________________    M1   C1   0.01                                                                               1   f    12  f    11  f                                          M2 C2 0.03  48 f 120 c  16 e                                                  M3 C3 0.08 270 c 678 a,b,e 842 b,d                                            M4 C4 0.1 264 a,c,e 664 a,b,e 1024  b                                         M5 C5 0.2 186 a,c,e 548 a,c 650 d                                             M6 C6 0.3 190 c,f 378 a,e 378 a,e                                             M7 C7 0.4 152 c,e 262 e 280 e                                                 M8 C8 0.5 106 c,f 154 e 312 e                                               __________________________________________________________________________

Table 16 shows that at boron levels (calculated as a weight percentageof the acrylate-group containing portion of the adhesive compositionplus thickener) below about 0.03 wt. %, adhesion is reduced. At about0.03 wt. % boron the adhesion to polyethylene increases. Above about0.08 wt. % boron, adhesion to all substrates improves. At high levels ofthe complex, the lap shear strength was less but adhesion wasmaintained.

EXAMPLE 9

A series of adhesive compositions according to the invention wasprepared in which the monomer mixtures described in Table 17 below werepaired with corresponding curative mixtures shown below in Table 18. Themonomer mixtures and curative mixtures were prepared as described above.In Tables 17 and 18, the relative amounts of the different ingredientsare given in grams.

The amount of organoborane polyamine complex was varied in the adhesivecompositions. In order to maintain a 1:1 stoichiometry (i.e., ratio ofisocyanate groups to the combined number of hydroxyl and amine groups),the level of polyol and polyisocyanate was varied. The polyol included1% by weight DBTDL. The ratio of primary amine nitrogen atoms to boronatoms in the complex was 1:1.

                  TABLE 17                                                        ______________________________________                                        Monomer   MMA     BA         TMXDI PMMA                                         Mixture (g) (g) (g) (g)                                                     ______________________________________                                        M1        7.13    5.13       10.20 7.50                                         M2 7.13 5.13 10.30 7.50                                                       M3 7.12 5.12 10.30 7.50                                                       M4 7.11 5.12 10.30 7.50                                                       M5 7.10 5.11 10.30 7.50                                                       M6 7.08 5.09 10.30 7.50                                                       M7 7.06 5.08 10.40 7.50                                                       M8 7.04 5.07 10.40 7.50                                                     ______________________________________                                    

                  TABLE 18                                                        ______________________________________                                        Curative  TONE 0305 TEB*DYTEK A COMPLEX                                         Mixture (g) (g)                                                             ______________________________________                                        C1        14.90      0.029                                                      C2 14.90  0.086                                                               C3 14.80 0.23                                                                 C4 14.70 0.29                                                                 C5 14.40 0.59                                                                 C6 14.10 0.89                                                                 C7 13.80 1.20                                                                 C8 13.50 1.53                                                               ______________________________________                                    

As shown below in Table 19 a series of adhesive compositions wasprepared in which a monomer mixture was combined with its correspondingcurative mixture at a 2:1 weight ratio to show how varying the boroncontent in the adhesive composition affects lap shear strength. The lapshear strength of the adhesive compositions was tested and the failuremode analyzed as described above and with the results shown in Table 19.

                                      TABLE 19                                    __________________________________________________________________________                  Testing                                                                       TEFLON   Polyethylene                                                                           Polypropylene                                 Adhesive Composition                                                                        Lap Shear                                                                              Lap Shear                                                                              Lap Shear                                     Monomor                                                                            Curative                                                                           Wt. %                                                                             Strength                                                                           Failure                                                                           Strength                                                                           Failure                                                                           Strength                                                                           Failure                                    Mixture Mixture Boron (psi) Mode (psi) Mode (psi) Mode                      __________________________________________________________________________    M1   C1   0.01                                                                               0   f    0   f    0   f                                          M2 C2 0.03  0 f  21 f  0 f                                                    M3 C3 0.08 146 c,f 688 a,b,e 336 a,c                                          M4 C4 0.1 159 f 654 a,b,e 349 a,c                                             M5 C5 0.2 289 a,c 536 b,f 757 a,d                                             M6 C6 0.3 222 a,c 318 a,e,f 688 e                                             M7 C7 0.4 239 a,c,e 399 c,e,f 612 c,e,                                        M8 C8 0.5 270 c 414 c,e,f 770 d,c                                           __________________________________________________________________________

Table 19 shows that at boron levels (calculated as a weight percentageof the acrylate-group containing portion of the adhesive compositionplus thickener) below about 0.03 wt. %, adhesion is reduced. At about0.03 wt. % boron adhesion to polyethylene increases. Above about 0.08wt. % boron, adhesion to all substrates improves.

Predominantly acrylic adhesives are often accompanied by a distinct andpungent odor which can make them unpleasant to use. Quite desirably,however, the adhesive compositions of example 9 which, exclusive of thePMMA, were approximately 2/3 polyurethane/polyurea and 1/3 polymerizedacrylic, had significantly less odor yet still provided adhesion tovarious low surface energy polymers.

Example 9 also evidences the ability to tailor the adhesive compositionby varying the relative amounts of polyurethane/polyurea and acrylic inthe cured composition. The relative amounts that are desirable will beinfluenced by the intended application, some applications benefittingfrom a larger amount of acrylic, while others will benefit from a largeramount of polyurethane/polyurea. However, it is possible to providecompositions that have the advantages associated with a polyurethaneadhesive (e.g., toughness, abrasion resistance) yet still adhere to lowsurface energy polymers, even though polyurethane adhesives aretypically associated with bonding high surface energy substrates. Insuch compositions, the polyurethane/polyurea will comprise more than 50%of the adhesive. More generally, however, the cured compositions of theinvention may comprise from about 1 to 80% polyurethane/polyurea and,correspondingly, from about 20 to 99% acrylic, these percentages alsobeing derivable from the relative amounts of acrylic monomer and thecombined amount of polyisocyanate, polyol and polyamine in thepolymerizable composition.

EXAMPLE 10

Example 10 describes the performance of a conventional two-part acrylicadhesive that was modified to also include monomers that wouldpolymerize to polyurethane.

Part A:

14.70 g. TONE 0305 (with 0.05% by weight DBTDL)

28.60 g. HYPALON 30 (chlorosulphonated polyethylene from E.I. duPont deNemours and Company)

53.74 g. methyl methacrylate

0.85 g. cumene hydroperoxide

Part A was generated by dissolving the various ingredients in oneanother.

Part B:

22.50 g. BLENDEX B467

10.00 g. TMXDI

67.50 g. methyl methacrylate

4.50 g VANAX 808 (from Vanderbilt Chemical Co.)

0.0045 g. copper napthenate

Part B was generated by weighing the ingredients into a metal jar andmixing under room temperature, ambient conditions with an air-powered,high shear mixer until a brownish, translucent thixotropic fluid wasobtained having minimal or no agglomerates of the BLENDEX B467 (lessthan 5 minutes).

The two parts of the adhesive were then weighed into a jar at a ratio of1:1 by weight and lap shear strength test specimens were prepared asdescribed above but with a 72 hour room temperature cure (i.e., curedover a weekend). The lap shear strength was tested and the failure modeanalyzed as described above and with the results shown below in Table20.

                  TABLE 20                                                        ______________________________________                                        TEFLON      Polyethylene   Polypropylene                                      Lap Shear       Lap Shear        Lap Shear                                      Strength Failure Strength Failure Strength Failure                            (psi) Mode (psi) Mode (psi) Mode                                            ______________________________________                                        5      f        72        f      34      f                                    ______________________________________                                    

The adhesive cured to a hard, relatively tough, yellowish-brown materialthat gave low lap shear strengths and failed adhesively. Example 10shows the significant loss in performance, especially to low surfaceenergy polymeric substrates, that occurs when the adhesive compositiondoes not include an organoborane polyamine complex.

EXAMPLE 11

In example 11, a pair of two-part adhesives (each comprising a "Part A"and a "Part B") were formulated as follows:

Part A1:

2.50 g. PMMA

2.53 g. BA

3.53 g. MMA

1.44 g. TEB*DYTEK A organoborane polyamine complex having a 1:1 primaryamine nitrogen atom to boron atom ratio.

Part B1:

10.00 g. PMMA

1.25 g. TMXDI

12.03 g. BA

16.72 g. MMA

Part A2:

2.50 g. PMMA

6.06g. MMA

1.44 g. TEB*DYTEK A organoborane polyamine complex having a 1:1 primaryamine nitrogen atom to boron atom ratio.

Part B2:

10.00 g. PMMA

1.25 g. TMXDI

14.56 g. BA

14.19 g. MMA

"Part A" of each adhesive was prepared by dissolving the acrylicmonomers and PMMA in each other and then adding the organoboranepolyamine complex. The initial viscosity of the solution was littlechanged after adding the complex. "Part B" was prepared by mixing thevarious components together. Each "Part B" was then combined with itscorresponding "Part A" in a 4:1 weight ratio so as to provide 0.002 partboron per part by weight of the two-part adhesive composition. The lapshear strength of the two adhesive compositions was then testedimmediately after combining the two parts and the failure mode of thebonds were analyzed as described above and with the results shown belowin Table 21.

                  TABLE 21                                                        ______________________________________                                               Testing                                                                         TEFLON      Polyethylene                                                                              Polypropylene                                Adhesive Lap             Lap         Lap                                        Composition Shear  Shear  Shear                                             Part Part    Strength                                                                              Failure                                                                             Strength                                                                            Failure                                                                             Strength                                                                            Failure                            A B (psi) Mode (psi) Mode (psi) Mode                                        ______________________________________                                        A1   B1      154     c     284   a,e   796   d,e                                A2 B2 194 c 376 e 798 d,e                                                   ______________________________________                                    

The two adhesive compositions could be used to make bonds immediatelyafter blending "Part A" with its corresponding "Part B". Changes in theviscosity of the two parts (before mixing with each other) under ambientconditions were observed visually. After two days, the viscosity of each"Part B" had not changed appreciably. After one day, however, each "PartA" had become extremely viscous. After two days, Part A1 had becomerubbery and Part A2 had become a hard solid indicating that theorganoborane polyamine complex, whose presence is important forproviding adhesion to low energy plastic substrates, is notstorage-compatible with acrylic monomers because it causes them tobecome hard or rubbery in only a couple of days.

EXAMPLE 12

Two adhesive compositions according to the invention comprising, fromexample 8, monomer mixture 4 (M4) combined with curative mixture 4 (C4),and monomer mixture 5 (M5) combined with curative mixture 5 (C5) werestored in sealed vials under ambient conditions for about 3 weeks. Therewas no visible change in the adhesive compositions at the end of thestorage period. The lap shear strength of the two adhesive compositionswas tested at the end of the storage period using the proceduredescribed above and with the results shown below in Table 22 along withthe assessment of the failure mode. For comparison purposes, the testresults for the corresponding adhesive compositions from example 8 areshown in parentheses.

                                      TABLE 22                                    __________________________________________________________________________              Testing                                                                       TEFLON   Polyethylene                                                                           Polypropylene                                     Adhesive Composition                                                                    Lap Shear                                                                              Lap Shear                                                                              Lap Shear                                         Monomer                                                                            Curative                                                                           Strength                                                                           Failure                                                                           Strength                                                                           Failure                                                                           Strength                                                                           Failure                                        Mixture Mixture (psi) Mode (psi) Mode (psi) Mode                            __________________________________________________________________________    M4   C4   146  c   540  a,e 506  d,e                                              (264) (a,c,e) (664) (a,b,e) (1024)   (b)                                    M5 C5 194 c 418 a,e 560 d,e                                                     (186) (a,c,e) (548) (a,e) (650) (d)                                       __________________________________________________________________________

Even after 3 weeks of storage, the lap shear strengths were still verygood and the failure mode had not changed significantly. By contrast,the adhesive formulations of example 11 had become hard or rubbery afteronly two days. Thus, the two-part adhesive compositions of the inventioncan be combined in commercially useful mix ratios but still haveexcellent storage stability.

EXAMPLE 13

Two adhesive compositions were prepared to evaluate rate of strengthbuild-up. The monomer mixtures described in Table 23 below were pairedwith corresponding curative mixtures shown below in Table 24. Themonomer mixtures and curative mixtures were prepared as described above.In Tables 23 and 24, the relative amounts of the different ingredientsare given in grams. The polyol included 1% by weight DBTDL. The ratio ofprimary amine nitrogen atoms to boron atoms in the complex was 1:1.

                  TABLE 23                                                        ______________________________________                                        Monomer  MMA       BA     IPDI   HEMA  PMMA                                     Mixture (g) (g) (g) (g) (g)                                                 ______________________________________                                        M1       11.97     8.61   1.92   0.00  7.50                                     M2 11.37 8.18 2.39 0.50 7.50                                                ______________________________________                                    

                  TABLE 24                                                        ______________________________________                                        Curative     TONE 0305 TEB*DYTEK A                                              Mixture (g) COMPLEX (g)                                                     ______________________________________                                        C1           2.38      0.62                                                     C2 2.39 0.61                                                                ______________________________________                                    

As shown below in Table 25 adhesive compositions were prepared in whichmonomer mixture M1 was combined with curative mixture C1, and monomermixture M2 was combined with curative mixture C2, each in a 10:1 weightratio. Using each adhesive composition, 15 adhesive bonds were made withpolyethylene adherends and 15 bonds were made with polypropyleneadherends. At various time intervals after the bonds were made, the lapshear strength was tested following the procedure described above andwith the results shown below in Table 25.

                  TABLE 25                                                        ______________________________________                                        Adhesive Composition                                                                 M1 + C1          M2 + C2                                                      Lap Shear Lap Shear  Lap Shear                                                                             Lap Shear                                    Strength on Strength on Strength on Strength on                              Time Polyethylene Polypropylene Polyethylene Polypropylene                    (hours) (psi) (psi) (psi) (psi)                                             ______________________________________                                        1       4         2          4       7                                          2  26  16 110  46                                                             3  44  17  80 118                                                             4  70  98 212 418                                                             5 140 170 324 468                                                             7 122 260 618 688                                                             24  714 806 714 1006                                                        ______________________________________                                    

The rate of strength build-up of the adhesive compositions of theinvention can be advantageously and suprisingly accelerated by thepresence of a bireactive compound such as hydroxyethylmethacrylate.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of the invention. It should be understood that this inventionis not limited to the illustrative embodiments set forth herein.

The embodiments for which an exclusive property or privilege is claimedare defined as follows:
 1. A polymerizable composition comprising:(a)polymerizable acrylic monomer; (b) organoborane polyamine complex; (c)polyol; (d) polyisocyanate; and (e) optionally, an organic thickener. 2.A polymerizable composition according to claim 1 wherein thepolymerizable acrylic monomer is selected from the group consiting ofmonofunctional acrylate ester, monofunctional methacrylate ester,substituted derivatives of the foregoing, and blends of the foregoing.3. A polymerizable composition according to claim 1 wherein thecomposition comprises about 0.03 to 1.5 weight % boron, based on theweight of acrylic-group containing components and optional organicthickener in the polymerizable composition.
 4. A polymerizablecomposition according to claim 3 wherein the composition comprises about0.1 to 0.3 weight % boron, based on the weight of acrylic-groupcontaining components and optional organic thickener in thepolymerizable composition.
 5. A polymerizable composition according toclaim 1 wherein the organoborane polyamine complex has the structure##STR14## wherein: R¹ is an alkyl group having 1 to 10 carbon atoms;R²and R³ are independently selected from alkyl groups having 1 to 10carbon atoms and phenyl-containing groups; Am is a polyamine selectedfrom the group consisting of alkyl polyamine, polyoxyalkylenepolyamine,and the reaction product of a diprimary amine-terminated material and amaterial having at least two groups reactive with primary amine, whereinthe number of primary amine groups in the reaction mixture was greaterthan the number of groups reactive with primary amine; and the value ofv is selected so as to provide an effective ratio of primary aminenitrogen atoms to boron atoms in the complex.
 6. A polymerizablecomposition according to claim 1 wherein the polyol is selected from thegroup consisting of polyether polyol and polyester polyol.
 7. Apolymerizable composition according to claim 6 wherein the polyol ispolyalkylene oxide polyol.
 8. A polymerizable composition according toclaim 6 wherein the polyol is selected from the group consisting ofpolyethylene oxide polyol, polypropylene oxide polyol,polytetramethylene oxide polyol, ethylene oxide- and propyleneoxide-terminated derivatives of these materials, poly-εcaprolactone, andblends of the foregoing.
 9. A polymerizable composition according toclaim 1 wherein the polyisocyanate is a diisocyanate.
 10. Apolymerizable composition according to claim 1 wherein the organoboranepolyamine complex is soluble in the polyol, and the polyol is soluble inthe acrylic monomer.
 11. A polymerizable composition according to claim10 wherein the polyisocyanate is soluble in the acrylic monomer.
 12. Apolymerizable composition according to claim 1 further comprising eithera compound that has both a free-radically polymerizable group and agroup reactive with amine, or a material that reacts with thepolyisocyanate to form a compound that has both a free-radicallypolymerizable group and a group reactive with amine.
 13. A polymerizablecomposition according to claim 1 further comprising a hydroxylated(meth)acrylate.
 14. A polymerizable composition according to claim 1further comprising a polyurethane formation catalyst.